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7 5 -2 7 ,2 3 2
BARKQ, John W illia m , 1947PRIMARY PRODUCTION AND ECOSYSTEM METABOLISM
IN A LAKE MICHIGAN DUNE POND.
Michigan S ta te U n iv e r s ity , P h .D ., 1975
Ecology

Xerox University Microfilms,

Ann Arbor, Michigan 48106

PRIMARY PRODUCTION AND ECOSYSTEM METABOLISM
IN A LAKE MICHIGAN DUNE POND

By
John W illiam Barko

A DISSERTATION

Submitted to
Michigan S tate U n iv e rs ity
in p a r t i a l f u l f i l l m e n t o f the requirements
f o r the degree o f

DOCTOR OF PHILOSOPHY

Department o f Botany and P lant Pathology

1975

ABSTRACT

PRIMARY PRODUCTION AND ECOSYSTEM METABOLISM
IN A LAKE MICHIGAN DUNE POND
By
John W illia m Barko

Estimates o f the net primary p r o d u c tiv ity o f phytoplankton,
e p ip e l ic periphyton, and macrophytes o f a small (0 .2 5 h a .) shallow
(mean depth = 41 cm.) s o f t water (mean a l k a l i n i t y = 1.24 meq/1) pond
located in the sand dunes o f Lake Michigan, were independently made
using in s it u
macrophytes.

14

C methods f o r algae and harvest techniques f o r

Estimates o f gross a s s im ila tio n and ecosystem r e s p ir a ­

t io n were made w ith in l i g h t and dark metabolic chambers (250 1.
c a p a c ity ) in which the C0£ f l u x was measured w ith an i n f r a - r e d gas
a n alysis system.

Laboratory measurements o f photosynthesis in

Juncus b a l t i c u s , the dominant macrophyte, were used in the in t e r p r e ­
t a t io n o f diurnal and annual v a ria tio n s in photosynthesis observed
under natural cond itio ns.
E p ip e lic and planktonic a lg a l components o f the a u to tr o phic community were q u a l i t a t i v e l y s i m i l a r .

Both components were

dominated by the desmid, Cosmarium s p ., mucilage secretions o f which
were important in m aintaining a heavy a l g a l - b a c t e r i a l e p ip e lic mat
t h a t p e rs is ted throughout the y e a r.

The macrophyte component was

s tro n g ly emergent, submersed macrophytes c o n trib u tin g less than 0.5%

John W illia m Barko

to the biomass.

F lo a tin g and f l o a t i n g leaved macrophytes were

e n t i r e l y absent.

F a u n is t ic a lly , the pond was represented by a

v a r ie t y o f in v e r te b r a te organisms which were most abundant in the
flo c c u le n t sediments.
Macrophyte production was c a lc u la te d on the basis o f annual
changes in below ground biomass, which represented g re a te r than 90%
o f t o t a l macrophyte biomass on a dry weight basis.

Algal production

was c a lc u la te d by in te g r a tin g the area under annual p r o d u c tiv ity
curves with respect to tim e.

Whereas production o f phytoplankton

and e p ip e lic periphyton occurred throughout the y e a r , production o f
macrophytes was lim ite d to the growing season.
Peak net production o f the phytoplankton tem porally over­
lapped peak net production o f the macrophytes, both occurring during
the e a r ly summer.

Net production o f the periphyton increased r a p id ly

during midsummer and was maintained a t a r e l a t i v e l y high r a te through
e a r ly autumn.
Total net primary p r o d u c tiv ity o f the pond was

2
348 mg C/m /d a y , expressed as an annual mean d a i l y r a t e .

P ro d u c tiv ity

o f the macrophytes (61% o f t o t a l ) was g re a te r than t h a t o f the p e r i ­
phyton (26% o f t o t a l ) and th a t o f the phytoplankton (13% o f t o t a l ) .
During the study, the pond underwent seasonal transforma­
tio n s between autotroph ic (P/R > 1 .0 ) and h e terotro phic (P/R < 1 .0 )
m etabolic modes.

Gross photosynthesis exceeded r e s p ir a tio n during

the growing season; the reverse s it u a tio n occurred during the dormant
season.

Annual mean d a il y gross p r o d u c tiv ity (547 mg C/m /d ay )

exceeded the annual mean d a il y r a te o f ecosystem r e s p ir a tio n

John W illia m Barko
2
(377 mg C/m /d a y ) .

The P/R r a t i o was estimated a t 1 .4 5 , in d ic a t iv e o f

2
net accrual a t the r a te o f 169 mg C/m /d a y , the annual mean d a ily

r a te o f net ecosystem production.
Gross photosynthesis was weakly c o rre la te d w ith day le n g th ,
e f f i c i e n c y , and s o la r energy, each tre a te d independently.

Annual

e f f ic i e n c i e s o f a s s im ila tio n (gross a s s im ila tio n /u s e a b le s o la r energy)
and growth (net production/gross a s s im ila tio n were estimated a t 0.42%
and 64% r e s p e c tiv e ly .
Annually, heterotrophic and auto tro p h ic components o f eco­
system r e s p ir a tio n were comparable, each accounting f o r approximately
h a l f o f the t o t a l r e s p ir a to ry a c t i v i t y .

During the growing season,

autotroph ic r e s p ir a tio n ( l a r g e l y a t t r i b u t a b l e to macrophyte a c t i v i t y )
represented 62% o f t o t a l r e s p ir a t i o n , whereas during the dormant
season, only 28% o f ecosystem r e s p ir a tio n was o f an autotrophic o r ig in .
P o te n tia l sources o f inaccuracy in vo lv in g methods used in
t h is study were discussed in a general c o n te x t, and more s p e c i f i c a l l y
w ith in the context o f t h is in v e s t ig a t io n .

The importance o f dissolved

organic m atter in aquatic systems was emphasized in regard to both
macrophyte p r o d u c tiv ity estimates based on harvest techniques, and
the in t e r p r e t a t io n o f P/R r a t i o s .
In conclusion, the dune pond is a r e l a t i v e l y unproductive
ecosystem, the net primary p r o d u c tiv ity o f which f a l l s w ith in ranges
o f values c ite d f o r some o f the less productive ecosystems o f the
world.

ACKNOWLEDGMENTS

I g r a t e f u l l y acknowledge the guidance o f my major professor,
Dr.

P eter G. Murphy, whose breadth o f knowledge and enthusiasm were

in v a lu a b le assets to me while conducting t h is study.

Dr. Robert G.

Wetzel and the Kellogg B io lo g ic a l S ta tio n deserve special recognition
f o r generously making s p e c ia lize d equipment and f a c i l i t i e s a v a ila b le .
Members o f my graduate committee, Dr. P eter G. Murphy, Dr. T. Wayne
P o r te r , Dr. Steven N. Stephenson, and Dr. Robert G. Wetzel, a l l con­
t r ib u te d valuable suggestions regarding the mechanics o f t h is study
as well as the manuscript i t s e l f .
Consideration is extended Jayashree Sonnad whose technical
assistance in the processing o f a lg a l samples is g r e a t ly appreciated.
During the in v e s tig a to ry stages o f t h is study, the patience
and encouragement o f my w i f e , Jane E. Barko, who also assisted me in
the preparation o f t h is manuscript, deserves s in g u la r re c o g n itio n .
Numerous in d iv id u a ls , fe llo w graduate students and o th e rs ,
a ssisted me in the f i e l d work and t h e i r help is

much appreciated.

In t h is regard I acknowledge S a n it Aksornkoae, Jim Coggins, John Dacy,
E ric Hansen, Dr. Glenn Kroh, Dr. Ken Mcleod, Dr. Brian Moss, P a t r ic ia
Paul us, Dr. Frank Reed, and Dave Tague.

The v i l l a g e o f Saugatuck,

Michigan provided access to the Saugatuck sand dune area in which the
research s i t e was lo ca te d .

ii

General equipment needs were provided by the Department of
Botany and P lant Pathology o f Michigan S tate U n iv e r s ity .

National

Canvas Products C orporation, Toledo, Ohio, generously provided the
P le x ig la s used in constructing metabolic chambers.

Recognition is

also due Mr. Leo W. Barnum and the L. E. L ig h th a rt and Company,
Lansing, Michigan, f o r providing hardware and o f f i c e equipment
re s p e c tiv e ly .

Portions o f the study were f i n a n c i a l l y supported by

AEC c o n tra c t AT ( 1 1 - 1 )-1 5 9 9 , COO-1599-94.

TABLE OF CONTENTS
Page
INTRODUCTION
GENERAL DESCRIPTION OF THE STUDY AREA
METHODS AND MATERIALS

.

1

..........................................

4

.............................................................

7

Net Primary P r o d u c tiv ity o f Phytoplankton ...................................
Net Primary P r o d u c tiv ity o f E p ip e lic Periphyton .........................
Macrophyte Biomass and P r o d u c tiv ity
..........................................
Ecosystem Metabolism ..................................................................................
Laboratory Determination Of Light Response
C h a ra c te ris tic s Of Juncus b a ltic u s ........ ..........................................

7
10
15
18
29

R E S U L T S .................................................................................................................

34

Description o f the Study P o n d ................................................
34
42
Algal Net Primary P r o d u c t i v i t y ................................................
Biomass and Net Primary P r o d u c tiv ity o f the Macrophytes
. .
Total Net Primary P ro d u c tiv ity o f the DunePond . . . . . .
Ecosystem Metabolism ...................................................................................
Lig h t Response C h a ra c te ris tic s o f Ouncus b a ltic u s
................

45
52
54
67

DISCUSSION.............................................................................................................

71

Algal P r o d u c t i v i t y .......................................................................................
Macrophyte Biomass and P r o d u c tiv ity ................................................
Ecosystem Metabolism ...................................................................................
Metabolic Im plic a tio n s Regarding Macrophyte P r o d u c tiv ity . .
Comparisons With Other Studies .............................................................

71
74
79
83
86

LITERATURE CITED ................................................................................................

89

L IS T OF TABLES
T a b le
1.

Page
Analysis o f Diurnal V a r ia tio n in Ecosystem
R espiration Rates ..........................................................................

23

Actual and P o te n tia l S olar Energy At Normal Incidence
In Southern Michigan ......................................................................

35

Seasonal V a ria tio n In Depth, Water, Temperature, pH,
and A l k a l i n i t y ...................................................................................

36

Diurnal V a r ia tio n In A ir Temperature, Water
Temperature, and pH..........................................................................

37

5.

Chemosynthetic Rates o f Dark F ix a tio n

....................................

45

6.

Seasonal Changes In Below Ground Proportion Of Total
Macrophyte Biomass ..........................................................................

48

Seasonal Changes In Ash Content Of Macrophyte Biomass
and L i t t e r ............................................................................................

50

Net Primary P r o d u c tiv ity (NPP):
Comparison o f
a utotroph ic communities in terms o f t h e i r
in d iv id u a l c o n trib u tio n s to the t o t a l net
primary p r o d u c t iv it y (TNPP) o f the dune pond ..................

53

In S itu Determination Of The Carbon Dioxide
Compensation Point For The Dune P o n d ...................................

58

Diurnal V a r i a b i l i t y In Rates Of Gross Photosynthesis
And Gross Photosynthetic E f fic ie n c y On F a ir Days . . .

59

Diurnal V a r i a b i l i t y In Rates Of Gross Photosynthesis
And Gross Photosynthetic E f fic ie n c y On An Overcast
Day In J u l y .......................................................................................

60

Seasonal In t e r r e la t io n s h ip s Between Gross Photo­
sy n th e s is , Indices Of Gross Photosynthetic
E f f ic ie n c y , Solar Energy, And Day Length . . . . . . .

61

Analysis Of Possible C o r r e la tiv e Factors A ffe c tin g
Gross P h o to s y n th e s is ......................................................................

62

2.

3.

4.

7.

8.

9.

10.

11.

12.

13.

Table
14.

15.

16.

17.

Page
Gross Photosynthesis And Ecosystem Respiration On
Harvested And Non Harvested Plots
.......................................

63

Ecosystem Metabolism:
Carbohydrate production and
degradation w ith in the dune p o n d ...........................................

65

Ecosystem Metabolic Indices:
Seasonal changes in
indices o f carbohydrate production and degradation
in the dune p o n d ..............................................................................

66

Annual Carbon Budget For The Dune P o n d ....................................

80

L IS T OF FIGURES
F ig u re

Page

1.

A r t i f i c i a l substrates used in periphyton study ..................

12

2.

Metabolic chambers used in gas exchange study

..................

19

3.

I n f r a - r e d gas a n alysis determination o f carbon
dioxide f lu x in l i g h t and dark c h a m b e r s ..........................

25

Metabolic chamber used in la b o ra to ry determinations
o f net photosynthesis in Juncus b a ltic u s ..........................

31

The net primary p r o d u c tiv ity o f algae is presented
f o r the period o f March 1973 through March 1974.
Monthly designations (abscissa) i d e n t i f y mid month
dates. Points represent the net primary produc­
t i v i t y o f phytoplankton ( 0 ) and e p ip e lic
periphyton ( A ) ..........................................................................

43

D is trib u tio n s o f macrophyte biomass and l i t t e r are
presented f o r the period o f A p ril 1973 through
October 1974. Monthly designations (abscissa)
i d e n t i f y mid month dates.
V e r tic a l bars represent
one standard e r r o r o f the mean v a l u e s ...............................

46

Ecosystem metabolism is presented f o r the period o f
July 1973 through October 1974. Monthly designa­
tio ns (abscissa) i d e n t i f y mid month dates.
Points
represent ra te s o f gross photosynthesis ( $ ) and
ecosystem r e s p ir a t io n ( A ) ....................................................

55

Net photosynthesis in Juncus b a ltic u s a t l i g h t
in t e n s i t ie s ranging between 0 and 5,500 fo o t
candles. Points represent net photosynthetic
rates in young ( $ ) and old stems ( A ) ........................

69

4.

5.

6.

7.

8.

INTRODUCTION

In "The Lake as a Microcosm," Forbes (1887) discussed the
interdependence o f plants and anim als, and in so doing, conceptually
described an aquatic ecosystem.

Subsequently, Lindeman (1942)

e lu c id a ted the functual nature o f t h i s interdependence, and Odum
(1962, 1963) modified the concept, more c l e a r l y s p e c ify in g the ro le
o f d e tritu s .
Concomitant w ith the development o f the ecosystem concept,
has been an increasing i n t e r e s t in the process o f primary produc­
tiv ity .

To d a te , most estimates o f aquatic primary p r o d u c t iv ity have

been based on phytoplankton s tu d ie s , r e f l e c t i n g the high degree o f
methodological refinem ent in t h i s area.

While approximating t o t a l

net primary p r o d u c tiv ity o f deep la k e s , p r o d u c t iv it y estimates based
s o le ly on phytoplankton, underestimate t o t a l p r o d u c t iv ity o f lakes
w ith a la rg e r a t i o o f c o lo n iza b le l i t t o r a l

zone to p elagic zone.

Due

la r g e ly to methodological c o n s tr a in ts , in s it u p r o d u c t iv it y estimates
o f attached algae and macrophytes have been meager.
of litto ra l

The s ig n ific a n c e

producers has been demonstrated in a shallow basin

(Borax Lake, W etzel, 1964) and in a r e l a t i v e l y deeper lake w ith a
moderate l i t t o r a l

zone (Lawrence Lake, Wetzel e t a l . ,

1972).

In the

comprehensive Lawrence Lake study, in co rp o ratin g the r e s u lts o f
several doctoral d i s s e r t a t io n s , net primary production o f the

macrophytes, periphyton, and phytoplankton r e s p e c t iv e ly , accounted
f o r 51.3%, 23.3%, and 25.4% o f the t o t a l net primary production o f
the la k e .
Community metabolism, in cluding hetero tro p h ic and auto­
tro p h ic processes, has been studied as an extension o f primary produc­
t i v i t y in v e s tig a tio n s .

Although lim n olo gists had been measuring

plan kto nic metabolism f o r years using the l i g h t - d a r k b o t t le oxygen
technique (Gaarder and Gran, 1927 ), the notion and th e o r e tic a l ram­
i f i c a t i o n s th e r e o f o r i g i n a l l y arose from the energy flow diagrams and
d e s c r ip tiv e c o n c e p tu a liza tio n o f Odum (1956 and 1957), and have since
been subsequently expanded upon by Margalef (1 9 6 8 ).
An extension o f the community metabolism concept is th a t
o f ecosystem metabolism which encompasses the in te g ra te d a c t i v i t y
o f in d iv id u a l communities w ith in an ecosystem.

Ecosystem metabolism

studies have been implemented in t e r r e s t r i a l systems using CO2 f lu x
models (see f o r example, Woodwell and W h itta k e r, 1968; Lemon e t a l . ,
1970).

Metabolic studies in l o t i c aquatic systems, using diurnal

oxygen techniques (Odum, 1965, M c D if f e t t e t a l . , 1972, and others)
and in l e n t i c systems using diurnal pH models (Verduin, 1952, 1956,
and o t h e r s ) , have measured community metabolism but not the metabolism
o f the e n t i r e ecosystem.

Cummins (1974) emphasized the heterotro phic

nature o f streams as processors o f allochthonous organic inputs from
the t e r r e s t r i a l watershed.

As such, a stream in i t s e l f cannot be

thought o f as an ecosystem, and metabolic measurements w ith in a
stream a r e , f o r the most p a r t , in d ic a t iv e o f the metabolism o f com­
ponent h e te ro tro p h ic communities.

S i m i l a r l y , studies o f l e n t i c

3

metabolism have g e n e ra lly been concerned with the a c t i v i t y o f s p e c ific
component communities, usually p la n k to n ic , and the re s u lts o f these
c e r t a i n l y cannot be e x tra p o la ted to the e n t ir e ecosystem.
Owing to conceptual and methodological advances in the areas
o f primary p r o d u c tiv ity and ecosystem metabolism, I have attempted to
in v e s tig a te the t o t a l p r o d u c tiv ity and metabolism o f an e n t i r e eco­
system (a dune pond).

S p e c if i c a ll y my ob je ctiv es in t h is study were

the fo llo w in g :
1.

The de s c rip tio n o f the dune pond ecosystem with regard
to p h y s ic a l, chemical, and b io lo g ic a l c h a r a c te r is tic s
r e le v a n t to oth e r aspects o f the study.

2.

The estim ation o f t o t a l net primary p r o d u c tiv ity .

3.

An evalu a tio n o f the importance o f the in d iv id u a l auto­
tro p h ic components with regard to t h e i r c o n trib u tio n s to
t o t a l net primary p r o d u c tiv ity .

4.

The estim ation

o f gross primary p r o d u c tiv ity .

5.

The estim ation

o f ecosystem r e s p ir a t io n .

6.

An evalu a tio n o f the r e l a t i v e magnitudes o f autotrophic
and h e terotro phic components o f ecosystem r e s p ir a t io n .

7.

The estim ation

o f net ecosystem p r o d u c tiv ity .

8.

The estim ation

o f gross photosynthetic and net photosynthe­

t i c e f f ic ie n c y w ith respect to s o la r energy and gross
a s s im ila t io n , re s p e c tiv e ly .

GENERAL DESCRIPTION OF THE STUDY AREA

The study s i t e was a small (0 .2 5 h a .) pond, located w ith in
the sand dunes o f Lake Michigan, near the Kalamazoo River d e l t a ,
Saugatuck, Allegan County, Michigan.

In view o f methodological con­

s id e r a tio n s , t h is pond was selected f o r study over other s im ila r
ponds in t h is area.

D e ta ile d d e s c rip tiv e inform ation on the study

pond, based on 18 months o f o b servation, is given in the re s u lts
section o f t h is t e x t .
The existence o f dune ponds, which are ubiquitous through­
out the Lake Michigan sand dunes, was f i r s t c ite d by Cowles (1899)
who conducted a d e s c rip tiv e survey on the vegetation and geology o f
the Lake Michigan sand dunes.

Cowles r e fe r r e d to them as " i l l

drained inland sloughs between r id g e s ."

Shelford (1911) discussed

successional aspects o f animal communities and b r i e f l y described
some o f the f l o r a l associations w ith in a v a r i e t y o f dune ponds located
in the Chicago area.

To my knowledge, there has been so subsequent

study o f the Lake Michigan dune ponds.
In the Saugatuck a re a , the ponds are p r i n c i p a l l y located in
the mid dune reg io n , e x is t in g approximately 150 meters inland from
the Lake Michigan shore l i n e .

These ponds have developed in depres­

s ions, formed by the scouring actio n o f the wind, and they p e r s is t as
aquatic h a b ita ts , dependent upon the Lake Michigan water l e v e l .
Considering the reduced le v e l o f the lake a t the turn o f the century

4

5

(S h e lfo rd , 1911 ), i t is u n lik e ly th a t these depressions were f i l l e d
a t th a t tim e.

However, t h e i r continual presence since the 1930's is

apparent in areal photographs taken during U.S. geological surveys
o f the area.

Dependent upon r a i n f a l l and water ta b le f lu c t u a t io n s ,

the mean depth o f the ponds is always less than 1 meter and usually
less than 50 cm.

Although the ponds are by no means ephemeral, the

presence o f remnants o f f u l l y t e r r e s t r i a l vegetation in shallower
a reas, suggests the occurrence o f occasional drought periods.
In c o n tra s t to the hard water o f Lake Michigan, the water
o f these ponds is r e l a t i v e l y s o f t , suggesting a mixture o f ra in
w ater and ground w ater.

Containing high concentrations o f p a r t ic u ­

l a t e d e t r i t a l m a t e r ia l, the h e a v ily s tra in e d water overlays a
f lo c c u le n t o r g a n ic a lly r ic h benthic s u b s tra te.
The macrophyte f lo r a is s tro n g ly emergent and submerged
l i f e forms occur sparsely and s p o ra d ic a lly only in l o c a l l y confined
deeper areas.

The t o t a l absence o f f lo a t i n g and flo a tin g - le a v e d

macrophytes is n o tab le.
d iv e rs e .

In g e n e ra l, the plankton is sparse and not

F l o r i s t i c a l l y , the plankton is s tro ngly dominated by

desmids, and f a u n i s t i c a l l y , r o t i f e r s dominate.

In c o n tra s t to the

p e la g ic zone o f these ponds, the benthos is well represented by
various in v e r te b r a te groups, aquatic and semi aquatic insects being
the most abundant metazoans.

Throughout most o f the y e a r , the pond

bottoms are covered by a th ic k mat o f periphyton, consisting o f a
m u c o -bacterio-algal a s s o c ia tio n .

P r e v a ilin g winds seem to be q u ite

e f f e c t i v e in preventing the establishment o f a lg a l associations

6

w ith in the emergent f l o r a , although e p ip h y tic associations do occur
in protected areas o f some o f the ponds.
The presence o f v e rte b ra te macrofauna in the ponds is q u ite
v a r ia b le .

Other than the p o te n tia l f o r n u tr ie n t enrichment by

m igrating w a te rfo w l, I suspect t h a t v e rtebrates have very l i t t l e
in flu e n c e on the ecology o f these areas.

The ponds appear to be

used by the nearby Kalamazoo River marsh fauna to absorb population
pressures and in t u r n , the r e l a t i v e l y s ta b le marsh area l i k e l y a ffords
refuge when drought periods threaten the existence o f the ponds.

The

t o t a l absence o f f is h is probably a t t r i b u t a b l e to anoxic conditions
incurred beneath the ice during severe w in te rs .
The t e r r e s t r i a l environment w ith in the Lake Michigan dune
region has been the o b je c t o f considerable in v e s tig a tio n w ith in the
past century.

Much o f the l i t e r a t u r e in t h is regard has been reviewed

by Mcleod, 1974, who conducted an autecological study o f the e s t a b lis h ­
ment o f the shrub, P t e l i a t r i f o l i a t a .

METHODS AND MATERIALS

Methods used in t h is study, in most cases, were selected
and modified in accordance with p i l o t in v e s tig a tio n s .

In a l l facets

o f the f i e l d s tu d ie s , data were c o lle c te d a t le a s t throughout an
annual c y c le .

A ll portions o f the pond were included in the

sampling design with the exception o f the w ate r-la n d in t e r f a c e
and a few hummock areas.

Net Primary P r o d u c tiv ity o f Phytoplankton
Phytoplankton p r o d u c tiv ity was estimated using the

14

C

technique, s l i g h t l y modified from t h a t o r i g i n a l l y introduced by
Steemann Nielsen (1951, 1952).

D e ta ils o f the modified technique

have been described elsewhere (Doty and O g u ri, 1959; S t r ic k la n d ,
1960; W etzel, 1966; among o th e r s ).

_In s jt u p r o d u c t iv ity measure­

ments were made a t two to three week in t e r v a ls from the 22 March
1973 through 11 May 1974.

A p re lim in a ry in v e s tig a tio n in d ic a te d

t h a t photosynthesis varied with depth, being g re a te r near the sub­
s t r a t e than a t the surface during the e a r ly s p rin g , but v a r ia t io n
was s t a t i s t i c a l l y in s i g n i f i c a n t between 4 b o ttle s incubated a t the
same depth a t d i f f e r e n t lo ca tio n s w ith in the pond.

Therefore a

s in g le sampling s ta tio n was used during the study and photosynthesis
measurements were made a t two depths.

7

Water samples c o lle c te d a t approximately 10 cm. below the
water surface and a t approximately 10 cm. above the pond bottom were
placed in to ground glass stoppered l i g h t and dark Pyrex b o ttle s
(125 m l . ) .

A 1 .0 ml. s o lu tio n o f Na2HC03 containing

known radioassay, 3 .5 to 4 .5 m ic rocuries/m l.

tr a c e r o f

(combustion and assay

in gas phase, Goldman, 1968) was in je c te d in to each b o tt l e which
was then sealed.

Three b o t t l e s , two c le a r and one dark, were pre­

pared and suspended a t each o f the two sampling depths.

A fte r a

s in g le midday 4 hr. in c u b a tio n , the b o ttle s were removed, placed in
a l i g h t - f r e e box and transported to the la b o ra to ry .

The p a r t ic u la t e

content o f the b o ttle s was resuspended by g entle shaking, and 25 to
50 ml. a liq u o ts were f i l t e r e d onto membrane f i l t e r s

(HA M il lip o r e

F i l t e r C orp., Bedford, Mass.) o f a p o ro sity o f 0.45± .02 microns
a t vacuum pressures o f 25-35 cm. Hg.

The pore s iz e o f 0.45

microns e f f e c t i v e l y removes a l l o f the phytoplankton (Lasker and
Holmes, 1957) and furthermore molecular f i l t e r s o f comparable pore
s ize have been r o u t in e ly used in phytoplankton s tu d ie s .

The f i l t e r e d

phytoplankton was d rie d in a desic c a to r and radioassayed with a m in i­
mum o f 2000 counts (o c c a s io n a lly 1000 counts f o r dark b o t t le a c t i v i t y
during the w in te r ) on a gasflow Geiger M u lle r counter (Nuclear
Chicago, Model 6010, w ith micromil window).
a ll

P r io r to radioassay,

f i l t e r s were decontaminated by exposure to fumes o f HC1 f o r

10 minutes (W e tze l, 1965a) although the necessity f o r t h is procedure
is questionable in s o f t waters.
Carbon a s s im ila tio n was c a lc u la te d by m u ltip ly in g the
assayed amount o f

14

C by the r a t i o between the t o t a l inorganic C o f

9

the pond water and the t o t a l inorganic

14

C added to the sample b o ttle s

before incubation (see V ollenw eider, 1969 f o r d e ta ile d o u tlin e o f
c a lc u la tio n s and parameters used t h e r e in ) .

A ll physical and chemical

d e term inations, necessary f o r a s s im ila tio n c a lc u la tio n s and subse­
quently used f o r d e s c rip tiv e purposes, were made a t pond s id e .

The

t o t a l inorganic C o f the pond water in m g ./ I. was c a lc u la te d from
the sample temperature (YSI Telethermometer, Model 46-TUC), the t o t a l
a l k a l i n i t y (chemical t i t r a t i o n , see American Public Health e t a l . ,
1 9 71 ), the pH (e le c tro m e tr ic d e term ination, Beckman, Model G), and
a p prop riate conversion fa c to rs (Saunders e t a l . , 1962).

An isotope

descrim ination f a c t o r o f 6 % was used in a l l c a lc u la tio n s (Steemann
N ie ls e n , 1955).

Non photosynthetic carbon f i x a t i o n (b a c te r ia l chemo-

synthesis and non b a c te ria l hetero tro p h ic carboxylation a c t i v i t y )
was compensated f o r in a l l c a lc u la tio n s o f photosynthesis by sub­
t r a c t i n g the dark b o t t le values from those o f the l i g h t .

Photosyn­

t h e t i c a s s im ila tio n was expanded from periods o f incubation to e n t ir e
sampling days using diurnal f a c t o r s , c a lc u la te d by planim etry o f the
s o la r energy curves (see W etzel, 1964; Jassby and Goldman, 1974) from
a recording Eppley p yrehelio m eter, operated a t the Kellogg B iological
S ta t io n , a distance o f approximately 65 km. from the research s i t e .
S i m i l a r l y , photosynthetic a s s im ila tio n was estimated between sampling
periods.
3

a rea l

Data are expressed both on a volum etric (per m ) and an
o
(p e r m ) basis.
Data on a volum etric basis were converted to

an areal b a s is , m u ltip ly in g by the mean pond depth on respective
sampling days.

Annual net primary production was determined by

10

in te g r a tin g the area under an annual p r o d u c tiv ity curve with respect
to tim e.

Net Primary P ro d u c tiv ity o f E p ip e lic Periphyton
Periphyton p r o d u c tiv ity was estimated using the

14

C tech­

nique, s l i g h t l y modified from t h a t used in e s tim ating phytoplankton
p r o d u c t iv it y .

In s it u p r o d u c tiv ity measurements were made a t two

to three week in t e r v a ls over the period from 14 A p ril 1973 through
20 A p ril 1974.

P re lim in ary in v e s tig a tio n s in d ic a te d the u n fe a s i­

b i l i t y o f sampling from the flo c c u le n t natural benthic substrate and
th e re fo re a r t i f i c i a l

substrates were employed.

The s u i t a b i l i t y o f a r t i f i c i a l
studies remains c o n tr o v e r s ia l.

substrates f o r periphyton

E ffo r ts devoted to assessing q u a l i t a ­

t i v e and q u a n t it a t iv e d iffe re n c e s between a r t i f i c i a l and natural
substrates (Pieczynska and Spodniewska, 1963; T i p p e t t , 1970) have
given c o n f l ic t in g r e s u lt s .

These studies d e a lt e x c lu s iv e ly with

e p ip h y tic a lg a l communities, and conclusions drawn from them are
probably less a p p lic a b le to benthic a lg a e , which may colonize sub­
s tra te s somewhat f o r t u it o u s ly w ith a le s s e r regard f o r substrate
type.

Wetzel (1965b) reviewed various problems w ith the use o f

a rtific ia l

substrates in p r o d u c tiv ity in v e s tig a tio n s and suggested

the placement o f a large number (enough f o r an annual study) o f
simulated sub s tra tes , a llow ing s u f f i c i e n t time f o r c o lo n iz a tio n
before sampling.
Microscope s lid e s , placed on the pond bottom in February
o f 1973, lacked the surface area necessary f o r buoyancy upon the

n
f lo c c u le n t sediments, sank in to the organic ooze and were abandoned.
On 4 March 1973, 60 la r g e r a r t i f i c i a l substrates were positioned on
the pond bottom a t one meter in t e r v a ls along two in te r s e c tin g
t r a n s e c ts , each being 30 m. in le ng th.

These substrates worked

e x c e p tio n a lly w e l l , remaining flu s h with the natural sediments
throughout the study.

They were constructed o f ceramic t i l e , 120 cm.

in a re a , o v e rla in with c ork, and wrapped w ith black polyethylene f i l m
(Figure 1 ).

The polyethylene f i l m f a c i l i t a t e d subsampling with a

cork bore minimizing major disturbance to the r e s t o f the t i l e com­
munity.

Backhaus (1967) reported e x c e lle n t r e p lic a t io n o f l o t i c

e p i l i t h i c periphyton on polyethylene f il m .
During each sampling p e rio d , fo u r t i l e s were randomly
selected from the tran sects f o r subsampling and then were qu ic kly
replaced on the pond bottom.

Polyethylene d is k s , 1.5 cm. in diam eter,

were removed from the t i l e s and placed in to l i g h t and dark ground
glass stoppered wide mouth Pyrex b o ttle s (125 m l . ) , previously f i l l e d
w ith u n f i l t e r e d and untreated pond w ater.
Na2HC0 2 containing the

A one ml. s olu tion o f

iso to p e , o f id e n t ic a l radioassay (same

l o t ) as t h a t used in the phytoplankton s tu d ie s , was in je c te d in to
the b o ttle s which were then sealed.

Four l i g h t b o ttle s and two dark

b o t t l e s , thus prepared, were immediately positioned on the pond
bottom, juxtaposed to those t i l e s from which t h e i r resp ective sub­
samples had been removed.

In the la b o ra to ry the a lg a l mass associated

w ith the polyethylene disks was dislodged, the disks removed from the
b o t t l e s , and any residual m a te ria l wiped from the disks onto f i l t e r s
designated f o r periphyton f i l t r a t i o n .

The p a r t ic u la t e content o f

12

Figure 1.

A r t i f i c i a l substrates used in periphyton study.

13

Figure 1.

14

the b o ttle s was suspended by shaking and the e n t ir e contents o f each
passed as 25 ml. a liq u o ts onto a s e ries o f f i v e 0 .45 micron Mi H i pore
filte rs .

Vacuum pressures were maintained a t 25-35 cm. Hg.

Occa­

s io n a lly during the summer, i t was necessary to mechanically disru p t
the massive a lg a l mat removed from the polyethylene disks in order
to uniform ly a llo c a t e the m a t e r ia l, reducing s e l f absorption d i f ­
fic u ltie s .

This was accomplished by p u llin g the mat through p ip e ttes

o f decreasing volume u n t i l the a lg a l m ate ria l e a s ily passed the
25 ml. p ip e t t e used f o r t r a n s f e r onto the f i l t e r s .
Post f i l t r a t i o n

la b o ra to ry trea tm e n t, radioassay procedures,

and carbon a s s im ila tio n c a lc u la tio n s were s im ila r to those described
f o r the phytoplankton samples.

The r a d i o a c t i v i t y e x c lu s iv e ly associ­

ated w ith carbon a s s im ila tio n by the periphyton was determined by
s u b tra c tin g the a c t i v i t y o f the phytoplankton from the sum o f the
a c t i v i t i e s o f the f i v e f i l t e r s

used per sample.

Volumes used f o r

d i s t r i b u t i o n and d i l u t i o n o f the a lg a l c e l l s were equated with the

2

o r ig in a l surface area colonized and the data expressed on a per m
basis.

Annual net primary production was determined by in te g ra tin g

the area under an annual p r o d u c t iv ity curve with respect to time.
Considering carbon a s s im ila tio n by both the phytoplankton
and the e p ip e lic perip h yto n , I have assumed t h a t the discrepancy
between

14

C uptake rates and the tru e rates o f a lg a l net primary

p r o d u c t iv it y are small as suggested by Ryther (1 9 5 4 ), Antia e t a l .
(1 9 6 3 ), and M c A llis te r e t a l . (1 9 6 4 ).

Due to the r e l a t i v e in accessi­

b i l i t y o f the research s i t e and the distance (approximately 60 km.)
between i t and the f i l t r a t i o n s i t e (Kellogg B iolo g ica l S t a t io n ) ,

15

unavoidable r e s p ir a to ry losses o f labeled substrate occurred during
tra n s p o rta tio n o f the sample b o ttle s in a l i g h t fr e e box.

Since

the time elapsing between b o t t l e r e t r i e v a l and la b o ra to ry f i l t r a ­
tio n approximated the incubation period (4 h r s . ) , I have chosen to
t r e a t r e s p ir a to ry losses during tra n s p o rt as a co rrec tio n f o r nig h t
r e s p ir a tio n (which was not measured in th is study) in converting
net p r o d u c tiv ity on a d a y lig h t hour basis to a d a ily (24 h r . ) basis.

Macrophyte Biomass and P r o d u c tiv ity
Seasonal changes in macrophyte biomass and p ro d u c tiv ity
were estimated by harvesting.

The harvest technique has been used

e x te n s iv e ly in aquatic systems to estim ate standing crop (see review
by W etzel, 1964).

Above ground p r o d u c tiv ity estimates have been

previously made by expressing standing crop on a seasonal basis
(Penfound, 1956; Forsberg, 1959; among o th e r s ).

Less fr e q u e n tly ,

due to the in herent d i f f i c u l t i e s o f below ground biomass sampling
(Westlake, 1968), t o t a l p la n t biomass estimates have been made.
P r o d u c tiv ity determinations based on t o t a l p la n t biomass, p a r t i c ­
u l a r l y in communities dominated by perennials with extensive rhizomal
portions (eg. Westlake, 1966; Bernard, 1974), are considered the most
meaningful.
Above ground biomass and l i t t e r were removed a t two to
three week in t e r v a ls over the annual period o f 14 A p ril 1973 through
20 A p ril 1974 w ith the exception o f the w in te r months (November to
February) and the 31 March 1974 sampling period during which the pond
was la r g e ly ice covered.

Below ground biomass was sampled a t two to

16
three week in t e r v a ls w ithout exception over the 18 month period o f
14 A p ril 1973 through 10 October 1974.

A ll sampling was done

randomly from fo u r tra n s e c ts , each being 30 m. in le n g th , two o f
which ran in a north-south d ir e c tio n and two in an east-w est d i r e c ­
t io n .
Above ground l i v i n g biomass and a l l l i t t e r was removed
2

by c lip p in g and raking from fo u r 0 .5 m frames, one from each t r a n ­
s ect.

Clipping was done as close to the substrate as possible

thereby minimizing under estimates o f c o n trib u tio n s by the stubble.
Immersed in a water f i l l e d basin, dead and l i v i n g m a te ria l was
c a r e f u l ly cleaned and separated in the la b o ra to ry .

No attem pt was

made to separate the p la n t m a te ria l in to taxonomic groups.

C o n tr i­

bution to the above ground biomass by taxa other than the two
dominants and w ith very few exceptions was minimal and u s u a lly zero
(see dune pond d e s c rip tio n in r e s u lts s e c tio n ).
Below ground biomass samples were obtained w ith a coring
2

auger, having a cross s ectional area o f 50 cm. , and capable o f
removing a core, 21 cm. in leng th.

Due to the nature o f the pond

bottom and the mode o f growth o f the rhizomal and rooted portions
o f the p la n ts , t h i s method was very e f f e c t i v e .

Below ground p la n t

m a te ria l grew l a t e r a l l y , r a r e ly exceeding 15 cm. o f depth in the
t i g h t l y compacted sand s o i l .

C utting c le a n ly through the extensive

rhizomal mat, the auger encountered the underlying compacted la y e r
o f sand which e f f e c t i v e l y sealed the p la n t sample w ith in the auger,
thereby preventing losses upon r e t r i e v a l .

Eight 100 cm.

2

samples

(two from each t r a n s e c t ) , each con s is tin g o f two cores, were taken

17

during each sampling p eriod .

In the la b o ra to r y , the samples,

contained w ith in a w ire mesh s t r a in in g s e iv e , were vigorously cleaned
o f the sand and associated organic de bris .

No attempt was made to

separate dead from l i v i n g below ground m a te r ia l.

Indeed the absence

o f metabolic a c t i v i t y in a submerged organ in no way precludes i t s
usefulness to the p la n t (Westlake, 1965).

Such organs may be impor­

ta n t as supportive s tru c tu re s and may also function in a storage
c a p a c ity .

Therefore a l l

below ground portions t h a t were strong

enough to remain i n t a c t a f t e r the washing process were tre a te d as
biomass.
To obtain dry weight estim ates, a l l macrophyte samples
(above and below ground) and the l i t t e r were dried f o r a minimum o f
24 hours in a forced a i r oven a t 100°C and weighted on a t r i p l e beam
balance.

These samples were then powdered in a Wiley m i l l , sub­

sampled, combusted in a m u ffle furnace a t 550°C and reweighed on a
to rs io n balance to obtain ash fr e e dry weight (organic weight)
estim ates.

Using a p prop riate areal conversion f a c t o r s , macrophyte
2

biomass was c a lc u la te d and is given as dry weight per m .

Converting

from organic weight to carbon weight using the f a c to r o f 0.465
(Westlake, 1965 ), macrophyte p r o d u c t iv ity is expressed as mgC/m
d a i l y and annual bases so t h a t i t may be compared to the algae in
determining r e l a t i v e c o n trib u tio n s o f in d iv id u a l autotroph ic com­
ponents to the t o t a l net primary p r o d u c t iv it y o f the dune pond
ecosystem.

on

18

Ecosystem Metabolism
In s it u estimates o f gross p r o d u c tiv ity and ecosystem
r e s p ir a tio n were made using a gas analysis technique based on carbon
dioxide exchange measured with an in f r a - r e d gas analy ze r (Beckman,
Model 215 A ).

Bordeau and Woodwell (1965) have reviewed in f r a - r e d

absorption techniques f o r measuring rates o f CC^ exchange.

This

technique f o r measuring C02 concentrations was selected over chemical
methods because o f i t s accuracy (Heath, 1969).
Two p o rta b le metabolic chambers, constructed o f 1 /8 inch
c le a r P le x ig la s (Figure 2) were used in the study to enclose portions
o f the pond f o r analysis o f ecosystem gas exchange.

These chambers

were id e n t ic a l in t h e i r dimensions, being one meter t a l l ,

?
1 /4 m in

cross sectional area (50 cm. x 50 cm .), and each having a volume o f
250 l i t e r s .

One o f the chambers (hence re fe rre d to as the dark

chamber) was wrapped with f i v e layers o f black polyethylene p l a s t i c ,
excluding a l l

lig h t.

Both were equipped w ith 1 /4 inch i n l e t and

o u t l e t p o rts , positioned opposite each o th e r , a t 25 and 75 cm. d i s ­
tances from the base.

The upper ports were used f o r gas withdrawal

and the lower f o r water c ir c u la t io n .
Due to the technical d i f f i c u l t i e s involved in f i e l d a p p lic a ­
tio n s o f the i n f r a - r e d analysis technique (Mooney e t a l . ,

1971 ),

p a r t i c u l a r l y in aquatic systems, gas samples were transported in gas
c o lle c t in g vessels to the la b o ra to ry f o r a n a ly s is .

A number o f gas

c o lle c t in g vessels were constructed f o r f i e l d use from 500 ml. glass
side arm f l a s k s , gum tu b in g , and compressor clamps.

These vessels

were r o u tin e ly autoclaved and oven drie d to prevent c o lo n iz a tio n o f

19

Figure 2.

Metabolic chambers used in gas exchange study.

20

Figure 2.

1

21
the inner surfaces by m icrobial organisms which, owing to t h e i r own
metabolic a c t i v i t y , would l i k e l y a f f e c t the analyses.

A check on

the i n t e g r i t y o f these c o lle c t in g vessels in terms o f t h e i r a b i l i t y
to r e ta i n q u a l i t a t i v e l y unchanged gas samples was performed by
f i l l i n g them with c a lib r a t io n mixtures o f 155, 309, and 455 ppm CO2
(balance n itro g e n ).

The q u a l it y (w ith respect to CO2 concentration)

o f these samples remained s t a t i s t i c a l l y (a = .0 5 ) unchanged f o r a
minimum o f 28 hours a f t e r which they slowly approached the ambient
(room) conc e ntra tion, undoubtedly through d i f f u s i v e exchange v ia the
tubing i n l e t - o u t l e t po rts.

During the course o f t h is study, the time

lag between gas sampling and analysis r a r e ly exceed 15 hours w ith the
exception o f three sampling periods in the summer o f 1973 during which
diurnal changes in ecosystem r e s p ir a tio n were monitored.
Determinations o f ecosystem metabolism were made a t 3 to 4
week in t e r v a ls (w ith few exceptions) over the 15 month period o f
6 July 1973 to 10 October 1974.

In order to avoid disturbed areas o f

the pond, as well as the a r t i f i c i a l substrates used f o r periphyton
sampling, the l i g h t and dark metabolic chambers were non randomly
positioned during each incubation period.

The two were always s i t u ­

ated adjacent to one another thereby insuring reasonable b io lo g ic a l
and physical homogeneity between them a t a p a r t i c u l a r s i t e .

The

water le v e l in the chambers r a r e ly exceeded 40 cm.; and the volume
o f the chambers occupied by water was g e n e ra lly less than 1 /3 o f the
t o t a l volume.
Measurement o f carbon dioxide in a closed system has the
disadvantage t h a t th is gas is the substrate used in forming

22
carbohydrates in photosynthesis.

Furthermore, in re a c tin g with

w ater, C02 forms a weak acid (^CO ^) which in a closed system may
create a pH change in co n s is ta n t with normal b io lo g ic a l fu n c tio n .

In

attempting to minimize the p o te n tia l in h i b i t o r y e f f e c t s o f very high
and very low C02 concentrations in the dark and l i g h t chambers
r e s p e c tiv e ly , incubation periods, ranging from 1/2 hour during the
e a r ly summer and 6 hours during the w i n t e r , were in v e rs e ly adjusted
to the metabolic a c t i v i t y o f the pond.
Normally the chambers were positioned f o r incubation pur­
poses a t 3 to 5 d i f f e r e n t positions throughout the pond between
08:00 and 20:00 during a sampling day.

At the beginning o f th is

study, incubations were performed d i u r n a lly w ith a t le a s t one n ig h t
time measurement.

Subsequent s t a t i s t i c a l a n a ly s is o f ecosystem

r e s p ir a t io n rates (Table 1) f a i l e d to demonstrate any d iffe re n c e s
between day and nig h t r e s p ir a to ry a c t i v i t y ; th e r e fo re n ig h t time
metabolic measurements were discontinued f o r the remainder o f the
study.
During each in cu bation , a i r and water temperature w ith in
both chambers was monitored a t in t e r v a ls o f 15 to 30 minutes using
a s ix channel telethermometer (Yellow Springs, Model 46-TUC).

D eter­

minations o f ambient a i r and water temperatures were s i m i l a r l y made.
Using a pressure-vacuum handpump (850 ml. c a p a c it y ), connected in
s e ries to the lower chamber p o r t a ls , the aqueous volume o f the two
chambers was p e r io d ic a lly c ir c u la te d to minimize a r t i f a c t u a l l y
induced s t r a t i f i c a t i o n p o t e n t i a l l y i n h i b i t i n g C02 d i f f u s i v e exchange
during longer incubation periods.

Using another handpump, o f

Table 1.

Analysis o f Diurnal V a ria tio n In Ecosystem Respiration Rates.

Morning Resp.

Noon Resp.

Date

mgC/m^/hr.

mgC/m^/hr.

Evening Resp,
p
mgC/m / h r .

Night Resp.
2
mgC/m / h r .

3 August 73

30.4

20.0

31.1

22.7

25 August 73

25.2

22.4

17.6

25.6

12 September 73

25.6

19.1

30.9

30.9

Average

27.0

20.5

26.5

26.4

Tukey's (LSR) M u ltip le Range T e s t ^

27.044

26.546

26.432

20.466

6.578

6.080

5.966

26.432

0.612

0.114

26.546

0.498

27.044

<1>LSR(.0 S ) - « ( 4 . 8 ) * 2 ' 74 = , 2 - 41
No d iffe re n c e s between collumn averages are s ig n if ic a n t a t 5% le v e l.

20.466

24

id e n tic a l design, gas samples were withdrawn in d u p lic a te from the
chambers in to gas c o lle c tin g vessels a t the commencement and a t the
end o f each incubation.

To avoid the p o s s i b i l i t y o f promoting

microbial a c t i v i t y under humid c o n d itio n s , gas samples were dried
by passing them through a d r i e r i t e column before in tro d u c tio n in to
c o lle c t in g vessels.

Both the c o lle c t in g vessels and the d r i e r i t e

column were connected in series with the handpump to the upper
chamber p o r t a ls .

Gas c o lle c tin g vessels were not disengaged from

the series u n t il the e n t ir e sampling system was brought in to q u a l i t a ­
t i v e e q u ilib riu m with the chamber sampled.

U su a lly , 30 to 40 l i t e r s

o f gas (50 depressions o f the handpump) were c ir c u la t e d through the
sampling system before sample removal.

At the end o f each sampling

day, the gas c o lle c t in g vessels were transported immediately to the
la b o ra to ry f o r CO2 a n a ly s is .
The i n f r a - r e d gas a n a ly z e r, coupled to a s t r i p chart
recorder (Honeywell, Model 1 9 3), was c a lib r a t e d using reference
gases o f 0, 155, 309, 455, and o c c a sio n a lly 600 ppm CO2
n itro g e n ).

(balance

By high a m p lific a tio n o f the a n alysis system, great

s e n s i t i v i t y (approximately 4 ppm COg) was a t t a in e d .

Reference and

sample gases were introduced in to the a n a ly ze r in a liq u o ts o f 20 c c . ,
using a gas t i g h t hypodermic syringe.

In response to the in tro d u c tio n

o f these gases, a s eries o f normal curves were generated (Figure 3 ) ,
the areas o f which were l i n e a r l y p rop ortional to the CO2 concentra­
tio n o f the reference gases adm inistered.

Using the recorder curves

associated with the reference gases, the areas beneath them ( d e t e r ­
mined by p lan im etry) were regressed on t h e i r resp ec tiv e CO2

25

Figure 3.

In f r a - r e d gas a n a ly s is determ ination o f carbon dioxide
f lu x in l i g h t and dark chambers.

30

20

600 PPM

455 PPM

309 PPM

155 PPM

20

10

ATMOSPHERIC
SAMPLE

LIGHT
CHAMBER
SAMPLE

DARK
CHAMBER
SAMPLE

ATMOSPHERIC
SAMPLE

FIGURE 3

LIGHT
CHAMBER
SAMPLE

DARK
CHAMBER
SAMPLE

ro
cr>

27

concentrations in developing l i n e a r p re d ic tio n equations (y = mx + b ) ,
used to c a lc u la te the CO2 concentration ( in ppm) o f the sample gases.
CO2 f lu x w ith in the t o t a l volume o f the chambers during
incubation was c a lc u la te d from e m p ir ic a lly determined changes in the
COg p a r t i a l pressure o f the gaseous volume (VG).

The C02 f lu x w ith in

VG was ca lc u la te d in mgC using equation 1.

Equation 1:

A mgC/VG = VG x

ppm CO,
(2)
Where:

537.714

x 1 *2 ^ (2)

II

-

.537.v7l l - | 9-C—
L i t e r (10 ppm)

I

x

ppm CO,
x
1 2(1)
TG(1)

= molecular
wt. o f carbon (mg) in one l i t e r o f
C
pure (10 ppm) CO2 .

ppm C0o

= in itia l

2 ( 1)
ppm C0o
(2 )

C0o p a r t i a l pressure.
2

= C0o p a r t i a l pressure a t the end o f incubation.
2

TG^ij

= in itia l

temperature (°K) o f VG.

TG^)

= temperature

(°K) a t the end

o f incu bation .

Considering the dynamic e q u ilib riu m e x is t in g between aqueous and
gaseous CO2 concentrations, the temperature dependent CO2 f l u x ra te
( i n mgC) w ith in the aqueous volume (VA ), was c a lc u la te d (equation 2)
knowing the gaseous f lu x r a te .

Equation 2:

A mgC/VA = (A mgC/VG) x

x AC f a c to r

In equation 2 , AC fa c t o r represents a r a t i o o f Bunsen absorption
c o e f f i c i e n t s , which adjusts the estim ate o f aqueous CO2 f l u x in

28

accordance with temperature dependent changes in the degree o f COg
s o l u b i l i t y during in cu bation .

When r e s p ir a t io n exceeds photosyn­

th e s is ( i . e . , dark chamber), AC f a c to r = (AC a t incubation end/AC a t
incubation i n i t i a t i o n ) .
(i.e .,

When photosynthesis exceeds r e s p ir a tio n

l i g h t chamber), AC f a c t o r = (AC a t incubation i n i t ia t io n /A C

a t incubation end).

CC^ f l u x w ith in the t o t a l volume (VT) o f the

chambers was c a lc u la te d in mgC using equation 3.

Equation 3:

A mgC/VT = ( A mgC/VG) + ( A mgC/VA)

A f t e r t h is summation, carbon f l u x was converted from a volumetric
p
basis (per 250 L . ) to an area l basis (p e r m ) , using approp riate
conversion f a c to r s .

Carbon f l u x was p o s itiv e w ith respect to ambient

concentration when r e s p ir a tio n exceeded photosynthesis ( i . e . , dark
chamber) and negative w ith respect to ambient concentration when
photosynthesis exceeded r e s p ir a t io n ( i . e . ,

l i g h t chamber).

G e n e ra lly , t h i s method was used to provide a s t a t i c (2
reference p o in ts ) ap p ra is a l o f the m e ta b o lic a lly mediated CO^ f lu x
occurring w ith in the ecosystem under natu ra l cond itio n s .

O ccasionally,

incubation periods were extended and gas samples removed i n t e r m i t ­
t e n t l y as well as a t the commencement and completion o f in cu b a tio n ,
in order to determine CO^ compensation c h a r a c t e r is t ic s o f the eco­
system.

The c a lc u la tio n s o f gross p r o d u c t iv it y and ecosystem

r e s p ir a tio n were e s s e n t i a l l y the same as those commonly employed in
oxygen l i g h t and dark b o t t l e determ inations o f phytoplankton com­
munity metabolism.

D i f f e r e n t i a l changes in the carbon concentration

w ith in the l i g h t and dark chambers during incubation were tr e a te d as

29

net ecosystem p r o d u c tiv ity and ecosystem r e s p ir a t io n r e s p e c tiv e ly .
Gross p r o d u c tiv ity was c a lc u la te d from the carbon d i f f e r e n t i a l
estab lis h e d between the l i g h t and dark chambers during incubation.

2
Metabolic data are expressed as means in mgC/m on ho urly,
d a i l y , growing season, and annual bases.

No r e la t io n s h ip was found

between s o la r energy and photosynthetic a s s im ila tio n (see re s u lts
section o f th is t e x t ) , th e r e fo re mean hourly ra te s o f gross photo­
synthesis were expanded to d a il y r a t e s , m u ltip ly in g by the number of
hours between sun-up and sun -s e t.

Annual mean rates o f gross produc­

t io n and ecosystem r e s p ir a t io n were determined by in t e g r a tin g the
area under annual curves with respect to tim e .

Annual mean net

ecosystem p r o d u c tiv ity was c a lc u la te d as the d iffe r e n c e between the
in te g ra te d ra te s o f gross production and ecosystem r e s p ir a tio n .
Growing season means were s i m i l a r l y determined.

Laboratory Determination o f Lig h t Response
C h a ra c te ris tic s o f Juncus b a ltic u s
Photosynthetic r a te in Juncus b a l t i c u s , the dominant emer­
gent, was estimated using a closed P le x ig la s gas exchange system with
a volume o f 12 l i t e r s .

The CC^ f l u x w ith in the system was con­

tin u o u s ly monitored using the same in f r a - r e d gas a n alysis and
recording equipment used in analyzing gas samples c o lle c te d during
in s i t u in v e s tig a tio n s .

The a n a ly z e r was c a lib r a t e d using gases o f

309, 155, and 0 ppm C0£ (balance n itr o g e n ).
A rtific ia l

l i g h t was provided by a bank o f two 500 w att

metal h a lid e f u l l spectrum bulbs and l i g h t i n t e n s i t i e s were measured
w ith a Weston E l e c t r i c Corp. fo o t candle meter a t distances o f

30

10, 20, 30, and 40 cm. w ith in a 60 cm. high c y lin d r ic a l metabolic
chamber (Figure 4 ) .

Changes in illu m in a t io n were f a c i l i t a t e d using

a varying rheostat connected in s eries w ith a S ta b lin e voltage reg­
u la t o r to the l i g h t bank.

The gas exchange system was cooled by

suspending the l i g h t source in a water f i l l e d P le x ig la s basin through
which cold tap water was c ir c u la t e d .

Temperature (telethermometer

determ inations) w ith in the photosynthetic chamber ranged from 22.0°C
a t the lowest l i g h t in t e n s i t y to 26.0°C a t the hig h e s t.

Gas flow

through the system was maintained a t the r a te o f 20 S .C .F .H . by reg­
u la t in g the output o f an a i r t i g h t pressure vacuum pump.
Several clones o f Juncus b a ltic u s were removed from the
dune pond on the evening before the day o f the experim entation.
These were c a r e f u l l y excavated in t h e i r e n t i r e t y (ro o ts and rhizomes
i n t a c t ) , placed in pond water f i l l e d buckets and transported to the
la b o ra to ry .

To avoid c u r lin g and breakage o f the apic a l t ip s in the

metabolic chamber, only the upper 60 cm. o f the stems were used in
these experiments.

The excision o f the upper 60 cm. po rtion o f the

stems and t h e i r placement in to a f la s k o f d i s t i l l e d w a te r, was done
immediately preceeding a n a ly s is .

In control experiments, McNaughton

(1973) has shown t h a t stem preparation as j u s t described has minimal
e f f e c t on both photosynthesis and t r a n s p ir a t io n .

Analyses a t nine

d i f f e r e n t l i g h t in t e n s i t i e s were performed once on 30 a r b i t r a r i l y
c la s s i f i e d o ld e r stems and once on 40 a r b i t r a r i l y c l a s s i f i e d younger
stems.

Wet weights o f p la n t m a te ria l were e s s e n t i a l l y equal with

respect to age categories analyzed.

31

Figure 4.

Metabolic chamber used in la b o ra to ry determinations o f
net photosynthesis in Juncus b a lt ic u s .

Figure 4.

33

Net photosynthetic r a te determinations as ppm C02 h r . ~ \
determined from the recorder output and a c a lib r a t io n curve, were
converted to mgCO^ h r . ” ^ using the fo llo w in g expression:
,
mgC02h r-

- ppm C O ^ r"

x 12 l i t e r s x

19 64 .28mgC0?
273° K
fe—
x chambgr at mos.
l i t e r ( 1 0 ppm)
temp/ o K

In t h is expression, 1964.28 represents the molecular weight o f C02
(as mg.) in one l i t e r o f pure (10 ppm) C02 a t S .T .P .
A ll rates o f net photosynthesis are given as mg C02 h r” "*
and are expressed on a dry weight basis (stems d rie d a t 100°C f o r
minimum o f 24 hours).

C02 compensation po in t determ inations, g raphi­

c a l l y derived from the c a lib r a t io n curve, are expressed as ppm C02<
Lig h t compensation p o in ts , determined g r a p h ic a lly from l i g h t response
curves (see r e s u l t s ) , are expressed in fo o t candles and in lu x .

RESULTS

D escription o f the Study Pond
During the study, s o la r f l u x a t normal incidence (Table 2)
was approximately 50% o f the p o te n tia l s o la r input (Kondratyev, 1969)
a t th is l a t i t u d e .

Lig h t measurements w ith in the water column were

not taken, and the e x te n t o f q u a l i t a t i v e and q u a n t it a t iv e a tten ua­
tio n o f l i g h t th e re in is not known.

Judging from i t s stained

appearance, the pond water is probably b o g -lik e w ith respect to i t s
l i g h t e x tin c tio n c h a r a c t e r is tic s (See The Fate o f Solar R a d ia tio n ,
in : R u ttner, 1952).

Observed annual and diurnal v a ria tio n s in

measured physical and chemical parameters are shown in Tables 3 and 4.
These data as well as subsequently described b io lo g ic a l fe atu res per­
t a in to the study pond (h e r e a f t e r r e fe r r e d to as "the pond"), and
can probably be e x tra p o la te d to some o f the nearby ponds, many o f
which d i f f e r only s l i g h t l y in morphometry, age, e tc .
The annual mean depth o f the pond during the period o f
A p ril 1973 through March 1974 was 41 cm.

During the summer o f 1974,

the mean depth was 11% less than t h a t o f the summer, 1973.

Depth

maxima and minima occurred during the summer and w in te r months
re s p e c tiv e ly , and d i r e c t l y c o r r e la t e w ith flu c t u a t io n s in the Lake
Michigan water le v e l

(USC0MM-N0AA-DC Lake Survey, 1974).

With few exceptions, the pond was not th e rm a lly s t r a t i f i e d .
Occasionally during windless mornings, p a r t i c u l a r l y on very hot

34

Table 2.

A c t u a l ^ And P o t e n t i a l ^

P o te n tia l Energy
Actual Energy
Percent ( A c t u a l/P o t e n t ia l)

Solar Energy At Normal Incidence In Southern Michigan.

A p ril 73 through March 7 4 ^

(4)
October 73 through September 74' '

187.9 kcal/cm^/year

187.9 kcal/cm^/year

94.8 kcal/cm^/year

2
97.0 kcal/cm /y e a r

50.5%

51.6%

^^Estim ated with an Eppley pyrheliom eter.
^ C a l c u l a t e d from global r a d ia tio n data (K. Ya. Kondratyev, 1969).
(3)
' 'Period during which annual net primary p r o d u c tiv ity was estimated.
^ P e r i o d during which annual gross primary p ro d u c tiv ity was estimated.

Table 3.

Seasonal V a r i a t i o n ^

Date
14
5
25
14
3
20
7
21
11
29
20
10
6
3
24
14
7
31
20
11
30
13
30
22
12
5
10

In Depth, Water Temperature, pH, and A l k a l i n i t y .

Mean D e p th ^ )(c m .)

A p ril 73
May 73
May 73
June 73
July 73
July 73
August 73
August 73
September 73
September 73
October 73
November 73
December 73
January 74
January 74
February 74
March 74
March 74
A p ril 74
May 74
May 74
June 74
June 74
July 74
August 74
September 74
October 74

38.0
46.0
50.0
47.5
51.5
43.0
45.0
55.0
42.0
43.5
43.5
39.0
45.0
38.0
4 4.0
33.0
35.0
39.0
39.0
38.0
4 5 .0
46.0
46.0
39.5
43.5
34.0
35.0

( 0 .5 )
( 2 .0 )
(1 6 .0 )
(1 0 .0 )
(1 0 .0 )

Water Temp.(°C)

pH

A l k a l i n i t y (meq/1.)

13.0
14.5
19.0
23.0
25.0
26.0
26.0
24.0
22.0
19.0
13.0
2 .0
1.0
0 .5
0.5
0.5
12.0
5.0
12.5
13.5
20.0
19.0
24.0
21.5
25.0
19.0
15.0

6.85
7.00
7.20
7.10
7.50
7.30
7.50
7.55
7.55
7.60
7.55
7.50
7.50
7.00
6.55
6.55
7.30
7.40
7.50
7.50
7.10
7.55
7.65
7.05
7.60
7.70
7.50

0.83
0.87
0.97
1.32
1.45
1.81
2.12
1.72
1.94
1.80
1.54
1.50
1.02
1.18
0.33
0.86
0.56
0.52
0.70
0.86
0.98
1.02
1.43
1.99
1.82
2 .10
1.60

^ D e t e r m in a t io n s made a t approximately noon during each sampling day.
^Num bers in parentheses represent ice thickness during w in te r months.

37

Table 4.

Diurnal V a r i a t i o n ^
and pH.

In A i r Temperature, Water Temperature,

Time

A ir Temperature(°C)

Water Temperature(°C)

pH

08:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00

12.0

17.5
19.0
2 0 .0
22.5
2 4.5
2 5 .0
2 4.0
2 2 .0

7 .40
7 .50
7.50
7.60
7.65
7.90
7.55
7 .50

24.0
28.0
1 2.0

^ D a t a from 12 September 73, a c le a r day exem plifying
observed ranges o f diurnal temperature and pH f l u x .

summer days, the upper water stratum would warm more q u ic k ly than the
lower, c re a tin g a 2° to 3°C temperature g r a d ie n t.

Such gradients were

q u ic k ly dissipated by a s l i g h t breeze, and normally were no longer
detec tab le by 10:00.

Diurnal water temperature f lu c t u a t i o n s , non

e x is ta n t during the w in t e r , and most notable during the spring and
f a l l , were g e n e ra lly on the order o f 5° to 10°C.

Maximum observed

ice thickness (1 6 .0 cm.) was observed in January during a period of
n e a rly continual ice cover (November 1973 through February 1974).
Temporary thawing occurred a t le a s t tw ice during the w in te r p r i o r to
the spring thaw in mid March.
During the annual period o f A p r il

1973 through March 1974,

the mean a l k a l i n i t y o f the pond water was 1 .24 meq/1.

Mean a lk a ­

l i ni t i e s during the summer o f 1973 and 1974 were comparable, being
1.48 and 1.39 meq/1. r e s p e c t iv e ly .

A nnually, the a l k a l i n i t y changed

s i g n i f i c a n t l y , ranging between w in te r minima and summer maxima,

38

observed maximal and minimal a l k a l i n i t i e s being 2 .12 and 0 .33 m eq.l.
r e s p e c tiv e ly .

V a r ia tio n in a l k a l i n i t y appeared to be associated with

changes in the le v e l o f the ground water t a b l e , caused by f lu c t u a ­
tio ns in the le v e l o f Lake Michigan.
To determine the inorganic carbon binding c apacity o f the
pond water r e l a t i v e to t h a t o f d i s t i l l e d w a te r, a la b o ra to ry check
was made by subjecting water samples o f increasing a l k a l i n i t y
( e q u ilib r a t e d with the atmosphere a t a constant temperature) to a
nitrogen purge, measuring the amount o f CO2 evolved w ith an i n f r a ­
red gas analysis system.

Pond water samples o f a l k a l i n i t i e s up to

approximately 1.60 meq/1. were not s i g n i f i c a n t l y (a = .05) d i f f e r e n t
from d i s t i l l e d water in terms o f t h e i r inorganic carbon binding
capacity.
Maxima and minima o f pH follow ed an annual p a tte rn id e n tic a l
to t h a t described f o r water depth and a l k a l i n i t y .

Observed midday

pH values ranged from a w in te r minimum o f 6 .50 to a summer maximum
o f 7.7 0 .

Diurnal flu c t u a t io n s in pH g e n e ra lly on the order o f 0 .2

to 0 .5 units during the summer, were not observed during the w in te r.
Both annual and d iurnal v a r ia t io n s in pH appeared to be stro ngly
r e la te d to water temperature change.
Observed atmospheric COg p a r t i a l pressure during d a y lig h t
hours ranged from a minimal summer value o f 285 ppm to a w in te r maxi­
mum o f 383 ppm.

Atmospheric COg concentrations were c o n s is ta n tly

higher during the n ig h t than during the day.

The annual mean, e s t i ­

mated from measurements during the day, was 336 ppm.

Dissolved

($ 2

approximations (c a lc u la te d from t o t a l a l k a l i n i t y , pH, and temperature

39

data; see R uttn e r, 1959) in d ic a te d annual supersaturation o f the pond
water w ith CO^ on the order o f 5 to 15 times atmospheric C0£ con­
c e n tr a tio n s , suggesting higher ra te s o f r e s p ir a tio n r e l a t i v e to
photosynthesis w ith in the water o f the pond.
The b io lo g ic a l s tru c tu re o f the pond can be o u tlin e d as
follo w s:
A.

Autotrophic community
1.

B.

Macrophytes
a.

Emergent

b.

Submerged

2.

E p ip e lic periphyton

3.

Phytoplankton

H eterotrophic community
1.

2.

In v e rte b ra te s
a.

Benthic

b.

Planktonic

Semiaquatic verte b ra te s

The emergent macrophyte f l o r a , homogeneously d is t r ib u t e d
throughout the pond, was represented by Juncus b a ltic u s and Cladium
m ariscoides, c o l l e c t i v e l y comprising 100% o f the emergent vegetation
sampled during the study.

P o te n tia l c o n trib u tio n s by Carex sp. and

Eleocharis s p ., interm ixed w ith t e r r e s t r i a l re presentatives along the
shore-water in t e r f a c e , were excluded by the sampling design as pre­
v iou sly discussed.

Juncus b a ltic u s and Cladium m ariscoides, exceed­

in g ly d i f f i c u l t to d is tin g u is h from one another v e g e t a t i v e l y , are
separable by f l o r a l and subtle rhizomal d iffe re n c e s ( F a s s e tt, 1957).

40

P r im a r ily on the basis o f rhizomal d if fe r e n c e s , since so few o f these
plants ever formed inflorescences during the study, I estim ate t h a t
g re a te r than 90% o f the emergent p la n t biomass war J_. b a l t i c u s .
Dominance by th is species in s im il a r Lake Michigan dune ponds has
been c ite d by Cowles (1899) and Shelford (1 9 1 1 ).
The tendency o f emergent plants to form pure closed com­
munities in h i b i t i n g c o lo n iza tio n by p o te n tia l competitors has been
discussed by Sculthorpe (1 9 6 7 ).

In t h is regard, plants which v ig ­

orously spread by means o f rhizomes, such as J. b a l t i c u s , may r e a d ily
r e a l i z e a dominant r o le where conditions fa v o r t h e i r exis ten c e.
The submerged macrophyte f l o r a was d im in u it iv e ly represented
by 111tricularia s p . , Chara s p . , F o n tin a lis s p . , and Potomaqeton sp.
R e i f f e r and Kleinsmith (1 9 7 3 ), conducting a d e s c rip tiv e survey o f the
pond as a class p r o je c t , estimated the c o n trib u tio n o f these plants
to the t o t a l standing crop a t less than 0.5%.

Rarely measureable in

those few samples in which they occurred, these plants c ontrib uted
very l i t t l e

to the biomass in th is study, and were tr e a te d w ith the

emergent f l o r a as previously discussed.
Dominant algal genera appeared to be represented in both
p elagic and benthic regions o f the pond.

The a lg a l community,

stro ngly dominated by Desmidacean r e p r e s e n ta tiv e s , in cluding Cosmarium
s p . , Staurastrum s p . , M ic ra s te ria s s p . , and Desmidium s p . , was subject
to l a t e summer invasion by Cyanophycean r e p r e s e n ta tiv e s , in cluding
Anabaena sp. and O s c i l l a t o r i a sp.

B acillariop hycean genera, i n f r a -

abundant throughout the season, assumed a very minor importance in
terms o f a lg a l biomass and, I suspect, p r o d u c t iv it y .

The

41

b a c te rio -a lg a l periphyton a s s o c ia tio n , e p ip e lic in nature f o r reasons
previously discussed, was s t r u c t u r a l l y dependent upon the copius
mucilage s ecretion o f Cosmarium s p ., the dominant alga w ith in the
pond.
Grazing and d e t r i t a l food processing pathways were com­
p l e t e ly dominated by in v e r te b r a te organisms, as is commonly the
case.

Observations on these in v e r te b r a te communities o f the pond

in dicated high d i v e r s i t y in s ta rk c o n tra s t to the f l o r a l u n ifo rm ity .
H o lo tric h c i t i a t e s , the dominant protozoan representa­
t i v e s , were complemented by the less abundant p e r i t r i c h s , both o f
which were p r i n c i p a l l y associated w ith the r ic h organic benthic
substra te.

Mastigophoran and sarodinian protozoans were found r a th e r

in fre q u e n tly .

R o t if e r s , e q u a lly abundant both upon the pond bottom

and w ith in the plankton, dominated the zooplankton community.
Oligochaete annelids occurred abundantly in the sediments, y e t
hirudinean re p re s e n ta tiv e s were t o t a l l y absent from the pond, perhaps
r e f l e c t i n g the p a u c ic ity o f p o te n tia l v e rte b ra te hosts.

The phylum

Arthropoda was meagerly represented by p la n k t o n ic a lly occurring
cladocerans and copepods, y e t was abundantly represented by various
taxa o f aquatic and semi a quatic in s e c ts , in clu d in g :

Odonata,

Coleoptera, D ip te ra , Hemiptera.
The most fr e q u e n tly encountered v e rte b ra te s were fro g s ,
several species o f which in ha b ite d the shore line region .

During the

spring o f 1974, a few p re v io u s ly unencountered mud t u r t l e s estab lished
residence in the pond.

O c c a s io n a lly , p a r t i c u l a r l y on stormy days,

m igrating ducks moved in from Lake Michigan, seeking temporary refuge

42

in the dune ponds and in the nearby Kalamazoo r i v e r marsh.

Located

on the eastern s h o r e lin e , a s in g le lodge, housed a t le a s t one muscrat
p a ir whose a c t i v i t i e s were la r g e ly r e s t r ic t e d to an adjacent much
shallower swale where they browsed on the younger shoots o f Carex
and E le o c h a ris .

There were no f is h in the pond, and I found no

evidence in d ic a tin g th a t any had ever been present.

Possible reasons

f o r t h is have alre ad y been discussed.

Algal Net Primary P r o d u c tiv ity
Seasonal pattern s o f net primary p r o d u c tiv ity o f phyto­
plankton and e p ip e l ic periphyton are presented in Figure 5.

Annual

mean d a ily rates o f net production o f phytoplankton and periphyton
2
2
were 4 6.6 mgC/m /d ay and 8 8 .7 mgC/m /d ay re s p e c tiv e ly .

The produc-

2

t i v i t y o f the phytoplankton ranged from 1 .6 mgC/m /day in mid w in te r

2
to 239.3 mgC/m /day in e a r ly summer and t h a t o f the periphyton from
2
2
4 .3 mgC/m /day in mid w in te r to 262.4 mgC/m /day in l a t e summer.
Although the ranges o f p r o d u c tiv ity values o f the periphyton and
phytoplankton were s i m i l a r , the d u ratio n o f peak periphyton produc­
t i v i t y was considerably g re a te r than t h a t o f the phytoplankton,
which on an annual b a s is , was only 52.5% as productive as the p e r i ­
phyton .
D iffe re nc e s in ra te s o f carbon a s s im ila tio n by the phyto­
plankton, i n s i g n i f i c a n t between b o ttle s incubated a t the same depth,
were s i g n i f i c a n t (a = .0 5 ) between b o ttle s incubated a t d i f f e r e n t
depths.

During the period o f May through October, a s s im ila tio n

w ith in the upper water stratum averaged 48% g re a te r than t h a t w ith in

43

Figure 5.

The net primary p r o d u c tiv ity o f algae is presented f o r
the period o f March 1973 through March 1974.

Monthly

designations (abscissa) i d e n t i f y mid month dates.

Points

represent the net primary p r o d u c tiv ity o f phytoplankton
(0 )

and e p ip e lic periphyton ( A ) .

A l g a l Ne t Pr i m a r y Pr o d u c t i v i t y

i

1------1"

O N

FIGURE 5

a

—

Ep i p e l i c

•

=

Ph y t o p l a n k t o n

D

Pe r i p h y t o n

i------1— i---- s— r

J

F

M

A

M

45
the lower.

Conversely, the opposite e f f e c t occurred without

exception during the period o f October through May, when a s s im ila ­
tio n by phytoplankton w ith in the lower water stratum was 74% g re a te r
than t h a t w ith in the upper.

V a ria tio n s in rates o f carbon a s s im ila ­

tio n between r e p lic a t e periphyton samples demonstrated no p a tte rn .
On an annual bas is , the c o e f f i c i e n t o f v a r i a b i l i t y ( S .D ./ x as a
percentage) averaged 27.2% ranging from 11.5% to 64.9%.
Annual pattern s o f benthic and plan kto nic dark f i x a t io n
mimiced pattern s o f l i g h t f i x a t i o n by the periphyton and phytoplankton.
Chemosynthetic rates o f dark f i x a t i o n (Table 5 ) , in te rp re te d as sec­
ondary p r o d u c tiv ity (see Sorokin, 1965) represented 4.2% and 13.1%
o f the annual mean l i g h t f i x a t i o n w ith in the planktonic and benthic
communities r e s p e c tiv e ly .

Table 5.

Chemosynthetic Rates o f Dark F ix a tio n .

Annual Mean
mgC/m2/day

% of
Carbon F ix a tio n in Lig h t

Benthic

11.6

13.1

Pelagic

2 .0

4 .2

Biomass and Net Primary P r o d u c tiv ity
o f the Macrophytes
D is trib u tio n s o f above and below ground biomass and l i t t e r
are given in Figure 6.

The below ground vegetation annually re p re ­

sented between 90.4% and 96.6% o f the t o t a l macrophyte biomass

46

Figure 6.

D is trib u tio n s o f macrophyte biomass and l i t t e r are
presented f o r the period o f A p r il 1973 through October
1974.

Monthly designations (abscissa) i d e n t i f y mid

month dates.

V e r tic a l bars represent one standard

e r r o r o f the mean values.

1400

1300
MACROPHYTE BIOMASS AND LITTER
1200
BELOW GROUND

1100
1000

-

D ry

We igh t

( gm /

m^

900
300
700
600
500
LITTER

320

160
ABOVE GROUND L IV IN G

80

FIGURE 6

48
(Table 6 ) .

L i t t e r was c o n tin u a lly p resen t, remaining a t le a s t three

times more abundant than above ground l i v i n g vegetation throughout
the study.

Table 6.

S e a s o n a l ^ Changes In Below Ground Proportion o f Total
Macrophyte Biomass.

Below Ground Biomass
(% o f t o t a l )
A p ril 73

96.6

May 73

96.0

June 73

96.5

July 73

94.1

August 73

90.4

September 73

91.3

October 73

-

November 73

-

December 73

-

January 74

-

February 74

-

March 74

96.2

^ A b o v e ground biomass harvesting discontinued between
October 1973 and February 1974.

During the 1973 growing season, above ground biomass, l i t t e r mass, and below ground biomass maxima o f 109 gm., 363 gm., and 1328 gm.
2

per m (dry w t . ) r e s p e c tiv e ly , were estim ated.

Periods o f above and

below ground biomass accrual did not correspond te m p o ra lly , the above
ground a c c ru a l, occurring in mid to l a t e summer, lagged behind t h a t

49
o f the below ground which occurred in l a t e spring to e a r ly summer.
L i t t e r mass increased s l i g h t l y during mid summer.
Pre-growing season measurements o f above ground biomass,
as well as l i t t e r , were not s t a t i s t i c a l l y (a = .0 5 ) d i f f e r e n t in
1973 and 1974.

2
A p ril measurements, expressed as dry w t./m , showed

40 gm. in 1973 and 38 gm. in 1974 present as above ground biomass,
and 263 gm. and 268 gm. present as l i t t e r mass during the same
periods.

Below ground biomass baselines d i f fe r e d s i g n i f i c a n t l y

however between 1973 and 1974, decreasing 35% from a mean value
(May da ta , 1973) o f 1139 gm. dry wt./m^ to a mean value o f 742 gm.
dry w t./m

2

c a lc u la te d during the same period in 1974.
C o e ffic ie n ts o f v a r i a b i l i t y ( S .D ./ x as a percentage) were

c a lc u la te d f o r biomass and l i t t e r determ inations.

A nnually, C.V.

values per sampling period averaged 18.9% f o r below ground biomass,
ranging from 7.3% to 31.1%; 19.9% f o r above ground biomass, ranging
from 5.2% to 38.6%; 20.5% f o r l i t t e r , ranging from 12.4% to 35.3%.
D is trib u tio n s o f C.V. values showed no p a tt e r n , inasmuch as the
magnitudes o f the values appeared to be seasonally independent.
Seasonal changes in the ash content o f above and below
ground biomass and l i t t e r are given in Table 7.

The ash contents

o f the above ground biomass and l i t t e r remained r e l a t i v e l y constant
a t 2% and 4% r e s p e c tiv e ly .

The ash content o f the below ground b io ­

mass e x h ib ite d a seasonal p a tte rn o f change, ranging from 8% during
the summer and f a l l months to as high as 15% during the spring.
As pointed out by Westlake (1 9 6 6 ), combustion o f p lan t
biomass provides a check on the adequacy o f root washing.

I t is

50
Table 7.

Seasonal Changes In Ash C o n t e n t ^ Of Macrophyte Biomass
And L i t t e r .
................. .

'

' " " "

« ■■

Above Ground

L itte r

Below Ground

A p ril 73

2%

4%

15%

May 73

2%

4%

9%

June 73

3%

4%

8%

Ju ly 73

4%

4%

8%

August 73

2%

4%

8%

September 73

2%

Mo

8%

October 73

-

-

8%

November 73

-

-

8%

December 73

-

-

8%

January 74

-

-

10%

February 74

-

-

10%

March 74

2%

5%

13%

A p ril 74

2%

Mo

14%

^ A s h content represented as percentage o f oven dry weight.

f e l t t h a t contamination o f below ground biomass samples by s o il
p a r t ic le s (sand) was n e g lig ib le in t h is study because the values f o r
ash content conform w ith s im ila r estimates c it e d in the l i t e r a t u r e
(see discussio n).
Estimating the p r o d u c tiv ity o f perennial macrophytes from
biomass s t a t i s t i c s is often problematical
techniques by Rich e t a l . , 1971).

(see a p p lic a tio n o f various

Generally a p p lic a b le models f o r

such estimates u n fo rtu n a te ly do not e x i s t .
In c a lc u la tin g the macrophyte p r o d u c t iv it y o f the dune pond,
several assumptions were made regarding the p a tte rn o f macrophyte
growth during t h is study.

50
Table 7.

Seasonal Changes In Ash C o n t e n t ^ Of Macrophyte Biomass
And L i t t e r .

Above Ground

L itte r

Below Ground

A p ril 73

2%

4%

15%

May 73

2%

4%

9%

June 73

3%

4%

8%

July 73

4%

4%

8%

August 73

2%

4#

8%

September 73

2%

4%

8%

October 73

-

-

8%

November 73

-

-

8%

December 73

-

-

8%

January 74

-

-

10%

February 74

-

-

10%

March 74

2%

5%

13%

A p ril 74

2%

4%

14%

^ A s h content represented as percentage o f oven dry weight.

f e l t t h a t contamination o f below ground biomass samples by s o il
p a r t ic le s (sand) was n e g lig ib le in t h is study because the values f o r
ash content conform w ith s im il a r estimates c it e d in the l i t e r a t u r e
(see disc u s s io n ).
Estim ating the p r o d u c tiv ity o f perennial macrophytes from
biomass s t a t i s t i c s is ofte n problematical
techniques by Rich e t a l . , 1971).

(see a p p lic a tio n o f various

Generally a p p lic a b le models f o r

such estimates u n fo rtu n a te ly do not e x i s t .
In c a lc u la t in g the macrophyte p r o d u c t iv it y o f the dune pond,
several assumptions were made regarding the p a tte rn o f macrophyte
growth during t h is study.

51
1.

Net photosynthetic a c c ru a l, as evidenced by the rapid and
s ig n i f i c a n t increase in below ground biomass, occurs
almost e x c lu s iv e ly during the e a r ly summer.

This was

substantiated by in s i t u and la b o ra to ry measurements o f
photosynthesis (discussed in a l a t e r section o f t h is
te s t).
2.

Losses due to g ra zin g , damage, and m o r t a l it y during th is
b r i e f period o f e a r l y summer production are n e g l ig i b le .

3.

The mid to l a t e summer increase in above ground biomass
is not an a d d itio n a l accumulation o f net primary produc­
tio n .

This accumulation, representing previously

a s sim ila te d photosynthate, r e f l e c t s the tra n s lo c a tio n o f
m a te ria ls from storage organs which provide a highly
l a b i l e pool f o r growth and stem replacement fo llo w in g
damage and m o r t a l it y .

Furthermore, t h i s pool is used as

a supplementary substrate f o r the increased r e s p ir a to ry
demands associated w ith senescence.

This assumption is

supported by the mid to l a t e summer p a tte rn o f below ground
biomass d e p letio n which tem porally corresponds with
increased above ground biomass production and l i t t e r
accumulation.

Furthermore, t h is period o f d epletion can

be associated w ith increased r e s p ir a t o r y a c t i v i t y by the
macrophytes (discussed in a l a t e r s e c tio n ).
To check the general p a tte rn o f below ground biomass change
observed in 1973, biomass determ inations were continued through the
1974 growing season.

Aside from the f a c t t h a t the mid summer

52
d epletion o f stored reserves from submerged organs was less pronounced
in 1974, the o v e r a ll p a tte rn repeated i t s e l f .

Macrophyte net pro­

d u c t i v i t y was c a lc u la te d on the basis o f below ground biomass change,
in co rp o ratin g fa c to rs f o r organic content (ash wt. determ inations)
and organic carbon content (0.4 6 5 recommended by Westlake, 1965).
P r o d u c tiv ity in 1974 was comparable to t h a t in 1973, being 239.3
2
2
mgC/m /d ay and 212.1 mgC/m /day r e s p e c tiv e ly .

Total Net Primary P ro d u c tiv ity o f the Dune Pond
The net primary p r o d u c tiv ity (NPP) o f the three autotrophic
components w ith in the pond are compared in Table 8.

To be tem porally

consistant with a lg a l p r o d u c tiv ity es tim ate s , macrophyte p r o d u c tiv ity
(as l i s t e d in Table 8) is based on data c o lle c te d during the 1973
growing season.

The t o t a l annual mean d a i l y NPP o f the pond was

2

347.4 mgC/m /day and production by the macrophytes accounted f o r
61.1% o f t h a t t o t a l .

Of secondary importance were the a lg a l com­

ponents, periphyton accounting f o r 25.5% and phytoplankton f o r 13.4%
o f the t o t a l .

93.1% o f t o t a l annual net production occurred during

the "growing season," a period o f approximately 160 days between
mid May and mid October.

The "growing season," as r e fe r r e d to in

t h is study, corresponds with the period o f net ecosystem production
(subsequently discussed).

Acknowledging the continued net production

o f algae during the "dormant season," the designation o f these two
seasons does not imply the contra ry.

Growing season mean d a ily

rates o f net primary production f o r a l l autotroph ic components were
approximately twice annual mean d a i l y ra te s .

Table 8.

Net Primary P r o d u c tiv ity (NPP): Comparison o f autotrophic communities in terms o f t h e i r
in d iv id u a l c o ntrib ution s to the t o t a l net primary p ro d u c tiv ity (TNPP) o f the dune pond.

Annual Mean

Growing Season Mean

D a ily R a t e ^
2
mgC/m /day

D a ily R a t e ^
2
mgC/m /day

% TNPP

Growing Season Prod.
x 100
% TNPP

Annual Production

Macrophytes

212.4

61.1

483.9

65.6

100.0

E p ip e lic
Peri phyton

88.7

25.5

161.5

21.9

79.8

Phytoplankton

46.6

13.4

92.3

12.5

86.9

347.4

100.0

737.7

100.0

93.0

TNPP

^ 3 6 5 day period (A p ril 1973 through March 1974).
^ 1 6 0 day period (May 1973 through October 1973).

54
Ecosystem Metabolism
Patterns o f gross photosynthesis and ecosystem r e s p ir a tio n
are presented in Figure 7 f o r the 15 month period o f 6 July 1973
through 10 October 1974.

Annual mean d a i l y ra te s o f gross photo2

synthesis, and ecosystem r e s p ir a t i o n , 546.7 mgC/m /d ay and 377.3

2

mgC/m /day r e s p e c t iv e ly , were c a lc u la te d f o r the 365 day period of
mid October 1973 through mid October 1974.

The annual mean d a il y

ra te o f net ecosystem production during the same p e rio d , c a lc u la te d
as the in te g ra te d d iffe r e n c e between rates o f gross photosynthesis
2
and ecosystem r e s p ir a t i o n , was 169.4 mgC/m /d a y .

Annual net eco-

O

system production (6 1 .8 gmC/m ) was 22.7% less than the growing

2

season accrual o f 8 0 .0 gmC/m .
During the study, the pond underwent seasonal transforma­
tio ns between autotroph ic (P/R > 1 .0 ) and h e te ro tro p h ic (P/R < 1 .0 )
metabolic modes, periods o f autotrophy and heterotrophy being q u ite
d is tin c t.

Autotrophic processes dominated between mid May and mid

October, the growing season, and h e terotro phic processes between mid
October and mid May, the dormant season.

The mid October conversion

from autotrophy to heterotrophy occurred w ith in approximately one
week o f the same conversion in 1973.

Since no gas exchange determina­

tio ns were made during the spring and e a r ly summer o f 1973, I can
only speculate on the temporal r e p e a t a b i l i t y o f the a lt e r n a t e con­
version (heterotrophy to autotrophy) which occurred in mid May 1974.
Judging from previously discussed pattern s o f net photosynthesis
however, i t is l i k e l y t h a t th is conversion s i m i l a r l y occurred some­
time during May o f 1973.

55

Figure 7.

Ecosystem metabolism is presented f o r the period o f July
1973 through October 1974.

Monthly designations

(abscissa) i d e n t i f y mid month dates.
ra te s o f gross photosynthesis ( 0
r e s p ir a t io n ( A

)•

Points represent

) and ecosystem

ECOSYSTEM METABOLISM

• z

Gross P h o t o s y n t h e t i c A s s i m i l a t i o n

▲z

Ecosystem R e s p i r a t i o n

cn
o>

0

N

0

F

FIGURE 7

M

A

M

i— i— r
A
S
0

57
Peak photosynthetic a c t i v i t y , occurring during thq e a r ly
summer, tem porally c o rre la te s with the rap id below ground biomass
accrual observed in June o f 1974.

R esp iration a c t i v i t y lagged

photosynthetic a c t i v i t y and peaked in mid J u ly .

Whereas ecosystem

r e s p ir a tio n was maintained throughout mid summer a t a somewhat
constant r a t e , the ra te o f gross photosynthesis was gra dua lly
a ttenuated.

Rapid reduction in ra te s o f both r e s p ir a tio n and gross

photosynthesis were observed in mid September, as the two processes
approached equivalence in mid October.

Gas exchange measurements

during the period o f w in te r ic e cover were complicated by conditions
o f reduced gaseous exchange with the atmosphere.

As a r e s u lt o f the

ice cover, impeding e q u ilib riu m , CO2 supersaturation o f the pond
water became r e l a t i v e l y extreme compared to t h a t occurring during ice
f r e e periods.

The CC^ released in to the m etabolic chambers, po si­

tioned in holes chopped through the ic e , accumulated a t rates on the
order o f 2 to 3 times maximal observed r e s p ir a t o r y ra te s .

As a

r e s u lt o f these c o n d itio n s , r e s p ir a to r y estim ates made during three
mid w in te r sampling periods were discarded and are not presented in
Figure 7.

Assuming th a t t h is phenomenon occurred s i m i l a r l y w ith in

both l i g h t and dark metabolic chambers, estimates o f gross photo­
s ynthesis, made under these c o n d itio n s , were not a f fe c te d .
Gas exchange measurements made during the summer o f 1973
(not used in annual or growing season metabolic ra te c a lc u la tio n s )
are believed to be underestimates caused by the extended incubation
periods (2 to 3 hours) used a t th a t tim e.

I t is apparent (Table 9)

t h a t photosynthetic r a te was in v e rs e ly r e la t e d to the duration o f

58

Table 9.

In S itu D e t e r m in a t io n ^ Of The Carbon Dioxide Compensation
Point For The Dune Pond.

L ig h t Chamber

Dark Chamber

5N

51^

Time

in ppm

in ppm/hr

in ppm

in ppm/hr

10:30

311

-

311

11:00

217

188

347

72

11:30

161

112

429

87

12:30

105

28

515

89

13:30

105

0

592

77

^ ^Data from 30 Cune 74.
Chambers placed in a s in g le p o si­
tio n a t 10:30.
Gas removal a t h a l f hour and one hour in t e r v a ls
during a 3 hour period.

in c u b a tio n , C0£ compensation achieved w ith in 2 to 3 hours during
periods o f a c t iv e photosynthesis.
little

Although r e s p ir a to r y r a te was

a f fe c te d by the duration o f in cu bation , extremely high dark-

chamber CO2 c oncentrations, associated with extended incubation
during mid to l a t e summer periods o f increased r e s p ir a to ry a c t i v i t y ,
produced a p o te n tia l f o r inaccuracy in the analysis o f subsamples,
the CO2 concentrations o f which were too high (> 600 ppm) to
a c c u ra te ly measure w ith the a n a ly s is system.
Diurnal pattern s o f gross photosynthesis and the e f f ic ie n c y
o f gross photosynthesis in r e l a t i o n to s o la r energy are presented in
Table 10 f o r selected c le a r to p a r t l y cloudy sampling days during the
summer o f 1973 and 1974.

Gross photosynthesis and, more s tro n g ly ,

the e f f i c i e n c y o f gross photosynthesis demonstrated morning and
evening maxima, the morning maxima being more pronounced than t h a t

Table 10.

Diurnal V a ria b ility In Rates Of Gross Photosynthesis And Gross Photosynthetic Efficiency
On Fair D a y s .^

Date
13 June 74

30 June 74

23 August 73

12 September 73

Solar Energy
2
gm cal/cm / h r

E ffic ie n c y

Time o f Day

Gross Photosynthesis
2
mgC/m / h r

10:00

176

27

6.46

12:00

126

27

4.65

14:00

114

35

3.24

16:00

98

35

2.79

09:00

138

24

5.68

11:00

121

42

2.90

14:00

100

64

1.55

15:00

63

65

0.97

08:00

48

10

4.67

11:00

57

50

1.16

13:00

59

49

1.20

19:00

51

18

2.88

09:00

72

23

3.13

13:00

59

59

1.01

18:00

64

29

2.21

In d e x ^

^ D a t a selected from c le a r to p a r t ly cloudy sampling days during the summers o f 1973
and 1974.
mgC/m2/d ay) per (gm cal/cm2/day) = gross photosynthesis/solar energy.

60

o f the evening.

Gross photosynthesis and the e f f i c i e n c y th e re o f

appeared to be in v e rs e ly r e la te d to s o la r energy during thes§ sampling
periods.

On h e a v ily overcast days, represented by 22 July 1974

(Table 1 1 ), tem porally r e la te d diurnal patterns o f gross photosyn­
th e s is and gross photosynthetic e f f i c i e n c y were no longer e v id e n t,
as increased photosynthesis became more s tro ngly dependent upon s o la r
energy a v a i l a b i l i t y .

Table 11.

Diurnal V a r i a b i l i t y In Rates Of Gross Photosynthesis And
Gross Photosynthetic E f f ic ie n c y On An Overcast Day In
J u ly .)

Gross Photosynthesis
Time o f Day

mgC/n/Vhr

Solar Energy
2
gm cal/cm / h r

E ffic ie n c y
In d e x ^

10:00

76

19

3.99

12:00

77

9

8 .18

13:00

58

7

8 .1 4

14:00

42

4

10.58

^ E x t r e m e l y heavy cloud cover and r a in throughout the day
(22 July 1974).

(2

) 2
2
(mgC/m /d a y ) per (gm cal/cm /d a y ) = Gross photosynthesis/

s o la r energy.

Annual in te r r e la t io n s h ip s between gross photosynthesis,
gross photosynthetic e f f i c i e n c y , s o la r energy, and day le n g th , are
given in Table 12 f o r sampling periods between 13 October 1973 and
10 October 1974.

The d i s t r ib u t io n o f s o la r energy was g e n e ra lly

r e la te d to t h a t o f day leng th.

However, because the sampling schedule

was implemented, in most cases, ir r e s p e c t iv e o f weather c o n d itio n s ,

Table 12.

Seasonal Interrelationships Between Gross Photosynthesis, Indices of Gross Photosynthetic
Efficiency, Solar Energy, And Daylength.

(2)
Gross Photosynthesis' '
?
mgC/m /day

Date
13
11
6
3
24
14
7
31
20
11
30
13
30
22
12
5
10

October 73
November 73
December 73
January 74
January 74
February 74
March 74
March 74
A p ril 74
May 74
May 74
June 74
June 74
July 74
August 74
September 74
October 74

437
148
74
105
24
67
45
68
0
82
655
1967
1614
1007
1407
1240
466

Solar Energy
2
gm cal/cm /day
100
61
75
78
221
250
380
323
543
159
252
445
572
104
473
380
235

E ffic ie n c y
In d e x ^
4.37
2.42
0.99
1.35
0.11
0.27
0.12
0.21
0.0 0
0.52
2.60
4.42
2.82
9.68
2.97
3.26
1.98

( 1)

' 'Gas exc-iange sampling dates.
2)
' 'C alculated by m u ltip ly in g mean uptake by daylength.

(

(11

2
2
(mgC/m /d ay ) per (gm cal/cm /d ay) = gross photosynthesis/solar energy.

(4)
v 'Hours between sunrise and sunset.

Daylength(4)
• 1 1 .0 0

9.92
8.07
9.08
9.80
10.50
11.50
12.67
13.60
14.50
15.10
15.32
15.30
14.85
14.08
13.00
11.00

62
gas exchange measurements were made under a v a r i e t y o f s o la r energy
conditions.

Gross photosynthetic e f f ic ie n c y was g re a te s t during the

growing season and le a s t during the dormant season, being gra dua lly
attenuated during the f a l l months to w in te r values an order o f magni­
tude lower than those o f the summer.

An analysis o f possible

c o r r e l a t i v e fac to rs a f f e c t in g gross photosynthesis (Table 13) revealed
weak r e la tio n s h ip s between i t and day le n g th , e f f i c i e n c y , and s o la r
energy, each tre a te d independently.

Gross photosynthesis was best

c o r r e la te d w ith day length and le a s t c o rre la te d w ith s o la r energy.

Table 13.

A n a l y s i s ^ Of Possible C o r re la tiv e Factors A ffe c tin g Gross
Photosynthesis.

C o rre la tio n
Gross Photosynthesis^ ^ and Daylength^ ^
(41
Gross Photosynthesis and E ffic ie n c y In d ic e s ' '
(51
Gross Photosynthesis and Solar Energy' '

C o rre la tio n
C o e f f ic ie n t ( r )
0.66
0.57
0.39

^ L i n e a r regression analyses.

^mgC/m^/day.
(31
' 'Hours between sunrise and sunset.
(41
2
2
' '(mgC/m / day) per (gm cal/cm /d ay ) = Gross photosynthesis/
s o la r energy.
(5)
2
'gm cal/cm /d ay.

To examine the e f f e c t o f above ground macrophyte biomass
removal on ecosystem metabolism, gas exchange determ inations were made
on harvested s it e s (Table 14) a t in t e r v a ls o f approximately 4 months

63

Table 14.

Gross Photosynthesis And Ecosystem R esp iration On
H a r v e s t e d ^ And Non H a r v e s t e d ^ P lo ts .

Gross Photosynthesis
2
mgC/m /day

Ecosystem Respiration
2
mgC/m /day

777

639

81

694

437

455

65

414

1405

902

11

170

1240

556

1

118

9 September 73
Nonharvested
Harvested
13 October 73
Nonharvested
Harvested
12 August 74
Nonharvested
Harvested
5 September 74
Nonharvested
Harvested

(1 )
v ' "Harvested" r e fe rs to those p lo ts which were disturbed by
the complete removal o f macrophyte above ground biomass and l i t t e r in
June and July 1973.

2)
v '"Non harvested" p lo ts contained i n t a c t communities.
(

and 15 months a f t e r removal during June and July o f 1973.

Ecosystem

r e s p ir a t io n approximately 4 months a f t e r removal, appeared to be
u n affe c te d , im p lic a tin g the remaining below ground biomass, associated
stubble and the decomposition t h e r e o f in the maintenance o f continued
r e s p ir a to r y a c t i v i t y .

Approximately 15 months a f t e r removal however,

the harvested plots were t o t a l l y devoid o f stubble and r e s p ir a to ry
a c t i v i t y had been reduced to 20% o f t h a t measured w ith in undisturbed

64
portions o f the pond.

The periphyton, perhaps dependent upon

m ic r o b ia lly mediated n u t r ie n t release from the l i t t e r , never e f f e c ­
t i v e l y recolonized s ite s which had been cleared o f n e a rly a l l
durinq the harvesting process.

litte r

Gross photosynthesis on the harvested

s ite s was d r a s t i c a l l y c u r t a i l e d , being almost immeasureable a f t e r
15 months, again r e f l e c t i n g the importance o f the macrophytes and
periphyton in the p r o d u c tiv ity o f the pond.
Annual and growing season mean d a i l y rates o f carbohydrate
production and degradation are summarized in Table 15, where autotro p h ic and he te ro tro p h ic components o f ecosystem r e s p ir a tio n are
independently presented.

Autotrophic r e s p ir a to r y rates were c a l ­

culated by s u b tra c tin g t o t a l net primary p r o d u c tiv ity from gross
primary p r o d u c t iv it y and hetero tro p h ic rates by s u btracting auto­
tro p h ic r e s p ir a t io n ra te s from ecosystem r e s p ir a t io n ra te s .

As

p rev io u s ly in tim ated by demonstrated seasonal patterns o f net photo­
s ynthesis, a utotroph ic metabolism appears to be la r g e ly lim it e d to
the growing season, 90.2% o f annual gross photosynthesis and 85.3% o f
annual a utotroph ic r e s p ir a t io n occurring during th is period.

In con­

t r a s t , only 58.6% o f annual hetero tro p h ic r e s p ir a t io n takes place a t
t h is tim e.

Consistent with the a r b i t r a r y designation o f "growing

season," 100% o f net ecosystem production occurs then.
Metabolic Indices (Table 16) were c a lc u la te d from photo­
synthesis, r e s p i r a t i o n , and s o la r energy data.
50% o f the t o t a l

I t was assumed t h a t

in s o la t io n , wavelengths between 390 and 760 nanno-

meters, can be used in photosynthesis (B ray, 1961; T a i l i n g , 1961).
Gross primary production was converted in to i t s c a lo r ic equiva len t

Table 15.

Ecosystem Metabolism:

Carbohydrate production and degradation w ith in the dune pond.

Annual Mean

Growing Season Mean

D a ily R a t e ^
2
mgC/m /day

D a ily R a t e ^
2
mgC/m /day

Gross
P r o d u c tiv ity

546.7

1125.4

90.2

Net Ecosystem
P r o d u c tiv ity

169.4

500.0

100.0

Ecosystem
Respiration

377.3

625.4

72.7

Autotrophic
Respiration

199.3

387.7

85.3

Heterotrophic
Respiration

178.0

237.7

58.6

^ 3 6 5 day period (October 1973 to October 1974).
^ 1 6 0 day period (May 1974 to October 1974).

Growing Season Prod, or Loss
x 100
Annual Production or Loss

Table 16.

Ecosystem Metabolic Indices: Seasonal changes in indices o f carbohydrate production
and degradation in the dune pond.
L = a v a ila b le s o la r energy; GPP = gross primary p ro d u c tiv ity ;
NPP = net primary p r o d u c tiv ity ; NEP = net ecosystem p r o d u c tiv ity ;
ER = ecosystem r e s p ir a tio n ; AR = autotrophic r e s p ir a tio n ;
HR = heterotrophic r e s p ir a tio n .

Annual B a s i s ^

(2)
Growing Season Basisv '

Dormant Season Basis' '

GPP/L

0.0042

0.0147

0.0018

npp / gpp ^4 '

0.64

0.66

0.45

GPP/ER

1.45

1.80

0.52

AR/ER

0.53

0.62

0.28

HR/ER

0.47

0.38

0.72

(3 )

^ 3 6 5 day period (October 1973 through October 1974).
^ 1 6 0 day period (May 1974 through October 1974).
^ 2 0 5 day period (October 1973 through May 1974).
^ I t is assumed th a t NPP during the 1973 growing season approximates NPP during the 1974
growing season.

67

using 4775 cal/gm. organic w t . , a compromise between values o f 4770
and 4780 suggested by Cummins and Wuycheck (1 9 7 1 ), f o r aquatic mono­
cots and green algae r e s p e c tiv e ly .

E f fic ie n c y indices were c a l ­

c ulated r e l a t i n g gross production to a v a ila b le s o la r energy a t the
pond surface (6 P P /L ), and t o t a l net primary production to gross
primary production ( NPP/GPP) .

Indices o f GPP/L and NPP/GPP have

been termed " a s s im ila tio n e f f ic ie n c y " and "growth e ff ic ie n c y "
re s p e c tiv e ly by Clarke (1946) and others.

A ssim ilation e f f ic ie n c y

was 0.42% a n n u a lly , varying between dormant and growing season
values o f 0.18% and 1.47% re s p e c tiv e ly .

Growth e f f i c i e n c y , 64%

a n n u a lly , varied between dormant and growing season values o f 45%
and 66% r e s p e c tiv e ly .

The r a t i o o f gross production to ecosystem

r e s p ir a t io n (GPP/ER) is commonly termed the "P/R r a t io " (Odum, 1956).
Annually, the P/R r a t i o was 1.45 varying between dormant and growing
season values o f 0.52 and 1.80 re s p e c tiv e ly .

Expressed as per­

centages o f ecosystem r e s p ir a tio n (ER) autotrophic r e s p ir a tio n (AR)
and h e te ro tro p h ic r e s p ir a tio n (HR) were q u ite s im il a r a n n u a lly , being
53% and 47% r e s p e c tiv e ly .

The dominant component (62%) o f ER during

the growing season was AR w h ile HR dominated (72% o f ER) during the
dormant season.

Light Response C h a ra c te ris tic s o f Juncus b a ltic u s
As prev io u s ly discussed, Juncus b a ltic u s was the dominant
macrophyte w ith in the dune pond.

Considering the demonstrated

importance o f the macrophytes in terms o f c o n trib u tio n to the metabo­
lism o f t h i s ecosystem, i t is f e l t t h a t photosynthetic c h a r a c t e r is tic s

68

o f th is species may be somewhat r e p re s e n ta tiv e o f the ecosystem
i t s e l f during the growing season.
The response o f each o f the two age categories o f stems
(young and o ld ) to increasing illu m in a t io n (Figure 8) was s im i l a r ,
y e t the net photosynthetic r a te o f the younger age category was
c o n s is te n tly g re a te r than t h a t o f the o ld e r a t a l l le v e ls o f
illu m in a tio n .
Unlike ty p ic a l l i g h t s a tu ra tio n curves (R ib in o w itc h , 1 9 5 1 ),
which beyond a l i n e a r l y ascending p o rtio n a t low l i g h t i n t e n s i t i e s ,
g radually ascend a s y m p to tic a lly , t h i s species demonstrated an abrupt
increase in slope between 3800 and 4500 fo o t candles (4 0 .9 to 4 8.4
k lu x ).

Considering the il lu m in a tio n g ra d ie n t w ith in the 60 cm. t a l l

photosynthetic chamber and the d i s t r i b u t i o n o f stem surface area o f
J. b a l t i c u s , which increases from the apex downward, i t is l i k e l y
t h a t l i n e a r l y ascending response a t low l i g h t in t e n s i t y occurred
asynchronously along the stem leng th.
Although l i g h t s a tu ra tio n was not t o t a l l y achieved in t h is
species a t 5500 fo o t candles (5 9 .2 k l u x ) , i t

is expected t h a t only

nominal increase in photosynthesis would be r e a liz e d a t higher l i g h t
in te n s itie s .

G ra p h ic ally e x tra p o la te d (Figure 8 ) , l i g h t compensa­

tio n occurred a t approximately 450 fo o t candles.

The C02 compensation

point (determ ination made a t 4500 fo o t candles) was 80 ppm C02 ,
approximately 24% less than an in s i t u compensation point determina­
tio n (105 ppm C02 ) made one week l a t e r (30 June 1974) under conditions
o f f u l l s u n lig h t and s im ila r temperature.

The high C02 compensation

p oint o f J. b a ltic u s suggests i t s possession o f the
pathway (Goldsworthy, 1970).

photosynthetic

69

Figure 8.

Net photosynthesis in Juncus b a ltic u s a t l i g h t in te n ­
s i t i e s ranging between 0 and 5,500 fo o t candles (0 to
59.2

k lu x ) .

in young ( 0 )

Points represent net photosynthetic rates
and old ( A

) stems.

70

Ne t Ph o t o s y n t h e s i s :

2.0

Young
of

a nd

J uncus

old

s te m s

b a l t ic u s .

Mg CC^/ gm/

hr

1.5

1.0

Young

15
A —

1
L ig h t

2

Ol d

s te m s

stems

3

in t e n s it y :

5
foot

candles

FIGURE 8

x

10^

DISCUSSION

Algal P r o d u c tiv ity
The seasonal d i s t r ib u t io n o f a lg a l p r o d u c tiv ity observed
in t h is study suggests a p a tte rn o f exchange between p lan kto nic and
e p ip e lic a lg a l populations s im il a r to t h a t reported by Brown and
Austin (1 9 73 ).

The taxonomic s i m i l a r i t y between these two com­

ponents o f the a utotroph ic community has a lre ad y been noted and
the p o s s i b i l i t y o f b i o lo g ic a lly o r physiochemically induced h a b it
transform ations should not be dismissed.

The phytoplankton pro­

d u c t i v i t y curve, being bimodal ( l a t e summer peak o f considerably
less importance than t h a t o f e a r ly summer) may in d ic a te c o lo n iz a ­
tio n o f the open water by a lg a l organisms g e n e ra lly r e s t r i c t e d to
the s u b s tra te.
The seasonal d is t r ib u t io n s o f both phytoplankton and
periphyton p r o d u c tiv ity might be explained by changes in the status
o f a v a ila b le n u trie n ts w ith in the pond.

Although d i r e c t determina­

tio ns o f the n u tr ie n t status o f the pond were not made, i t is f e l t
t h a t auto tro p h ic a c t i v i t y is lim it e d by a general p a u c ic ity o f
n u tr ie n t s .

Notably, the s o il o f the Lake Michigan sand dunes is

impoverished in t h is regard (Olson, 1958).

Algal growth in the pond,

subsequent to the e a r ly summer flu s h o f phytoplankton growth, is
la r g e ly lim it e d to the benthic substrate where m ic r o b ia lly mediated
n u t r ie n t release from the sediments may be stim ulated by r is in g

71

72
temperature (Hutchinson, 1957).

During l a t e summer, m icrobial

a c t i v i t y possibly provides a n u t r i e n t supply in excess o f e p ip e lic
a lg a l requirements, thus enabling the reestablishment o f the phyto­
plankton.

N u tr ie n t ( s i l i c a )

release from l i v i n g macrophytes has

been c it e d (J0rgensen, 1957) in the rapid growth o f diatomaceous
epiphytes fo llo w in g t h e i r c o in c id e n ta lly occurring exclusion from
the plankton due to s i l i c a d e p le tio n .
Surface in h i b i t i o n o f p lan kto nic a lg a l photosynthesis by
l i g h t o f high i n t e n s i t y has been w idely observed ( T a i l i n g , 1957;
Jonasson and Mathiesen, 1959; Goldman e t a l . , 1963; among o th e r s ).
L ik e ly unimportant in deep la k e s , t h i s i n h i b it io n may be s ig n i f i c a n t
in shallow basins (W e tze l, 1964).

The observed p a tte rn o f photosyn­

th e s is w ith respect to depth in the dune pond, counters t h is common
phenomena however, and is d i f f i c u l t to re so lv e .

The g re a te r photo­

s y n th e tic a c t i v i t y near the s u rfa c e , observed during the growing
season, would seem to be p a r t i a l l y explained by increased t u r b i d i t y
w ith in the lower stratum r e s u lt in g from the unavoidable a g it a t io n o f
the f lo c c u le n t substrate w h ile p o s itio n in g the sampling b o ttle s f o r
in s i t u in cu bation .

However, the converse (g r e a te r photosynthesis

near the s u b s tra te ) evidenced during the dormant season, occurred
under s i m i l a r l y disturbed c o n d itio n s .

The a r t i f a c t u a l s ta te o f

increased t u r b i d i t y was normally d is s ip a te d w ith in 0 .5 hour a f t e r
placement o f the sampling b o t t l e s , and i t is f e l t t h a t t h is problem
had a le s s e r e f f e c t on the v e r t i c a l d i s t r ib u t io n o f phytoplankton
p r o d u c t iv it y than the presence o f dissolved and p a r t ic u la t e humic

73

substances, which appeared to be most concentrated in the pond water
during the growing season.
Placement o f b o ttle s on the pond bottom f o r in s it u
incubation o f e p ip e lic periphyton samples re su lte d in the same condi­
tio ns o f temporary t u r b i d i t y as discussed in regard to the p o s itio n in g
o f phytoplankton b o tt le s .

During the study, great care was taken to

reduce the e x ten t and duration o f such conditions however, thereby
minimizing the p o te n tia l f o r underestimation o f photosynthesis due
to unnatural l i g h t a tte n u a tio n .

In regard to estimated rates o f

a lg a l photosynthesis (p lan kto n ic and b e n th ic ), the e f f e c t o f these
conditions on photosynthesis measurements is f e l t to be sm all.
P a r t i c u l a r l y r e le v a n t to t h is study, a p o t e n t i a l l y serious
source o f e r r o r in estim atin g the p r o d u c tiv ity o f e p ip e lic periphyton
a ris e s from the expansion o f small experim e n ta lly measured surfaces
to la r g e r areas.

P r o d u c tiv ity estimates based on small samples, may

not be e n t i r e l y r e p re s e n ta tiv e o f the whole, the p o te n tia l f o r e r r o r
increasing w ith substrate h eterogeneity.

The e p ip e lic periphyton in

t h is study appeared q u ite homogeneously d is t r ib u t e d however, and i t
is f e l t t h a t e r r o r involved in expansion from sample area to a square
meter basis was r e l a t i v e l y sm all.
S e lf absorption o f beta p a r t i c l e s , caused by la y e rin g o f
e p ip e l ic a lg a l m a te ria l on the membrane f i l t e r s , may have a ffe c te d
the counting during the l a t e summer period o f maximum periphyton
biomass.

During the remainder o f the y e ar however, la y e rin g o f the

sample m ate ria l was not a p p re c ia b le .

This problem may r e s u lt in

underestimated ra te s o f photosynthesis and can be circumvented by

74
combustion o f the organic m a te ria l f o r radioassay in gas phase
(W etzel, 1964), but th is approach is tedious and maximum sample size
is lim it e d .

Because o f t h is and oth e r tec h n ic a l d i f f i c u l t i e s involved

in benthic a p p lic a tio n s o f the

technique, many in v e s tig a to rs have

used the oxygen method (Pomeroy, 1959; Pamatmat, 1968; Hargrave,
1969; among o th e r s ).

In a recent paper (Hunding and Hargrave, 1973)

on the primary p r o d u c tiv ity o f benthic a lg a e , the two methods ( ^ C
and oxygen) were shown to give s im il a r r e s u lts and i t was pointed out
t h a t n e ith e r o f the two was f r e e from experimental a r t i f a c t s and
assumptions.

The

14

C method however has the advantage t h a t i t does

not necess itate the determination o f a photosynthetic q u o tie n t
(u s u a lly assumed), and furthermore i t may be the only s u ita b le method
where low production would be expected.

Macrophyte Biomass and P r o d u c tiv ity
Considering the dynamics o f growth and seasonal produc­
t i v i t y o f the macrophytes o f the dune pond, i t is important to
r e i t e r a t e t h a t Juncus b a ltic u s composed g re a te r than 90% o f the
a utotrophic biomass.

I t is f e l t ,

in f a c t , t h a t subsequent discussion

concerning the macrophytes is e s s e n t i a lly a treatm ent o f the dynamics
o f growth and p r o d u c tiv ity o f J. b a l t i c u s .
Laboratory in v e s tig a tio n s on Juncus b a ltic u s in d ic a te d a
decline in net photosynthetic p o te n tia l w ith l e a f age.

This decline

has been described in a v a r i e t y o f t e r r e s t r i a l species (Wilson and
Cooper, 1969; Osman and M ilth o rp e , 1971) and also in an aquatic
emergent, Typha l a t i f o l i a

(McNaughton, 1973).

These observations

75
may be a t t r i b u t e d to e-'ther increased r e s p ir a to r y demands or to
decreased carb oxylation a c t i v i t y in the o ld e r stems.

Both o f these

fa c to rs were l i k e l y important in r a p id ly c u r t a i l i n g macrophyte net
production by mid summer as determined using the harvest method.
Since both young and old shoots o f J. b a ltic u s demonstrated i d e n t i ­
cal COg compensation points (80 ppm) in la b o ra to ry in v e s tig a tio n s ,
seasonally decreased net photosynthetic p o te n tia l in the o ld e r
shoots was u n lik e ly r e la te d to increased r e s p ir a to ry demands w ith in
the shoots themselves.

I t is important to po in t out however t h a t

th is conclusion is not a p p lic a b le to whole p la n ts , since the "roots"
were not included in the la b o ra to ry measurements.

"Root" r e s p ir a ­

tio n very l i k e l y increased as the photosynthetic capacity o f the
macrophytes a ffe c te d by shoot senescence became reduced.
The importance o f the rhizomal and rooted portions o f the
macrophytes cannot be overemphasized in t h is study.

Below ground

portions annually represented > 90% o f the t o t a l macrophyte biomass.
S im il a r l y high values have been c ite d f o r Scirpus la c u s t r is and f o r
Phragmites communis, but the m a jo rity o f values given f o r other
"perennial reedswamp plants" are somewhat less (W estlake, 1965, 1968).
Boyd (1971) estimated the c o n trib u tio n by "roots" to the t o t a l
biomass o f Juncus effusus a t about 10%.

This value is probably too

low however, since root removal in the J. effusus study was not
s y s te m a tic a lly accomplished.

To my knowledge, no data e x is t on the

biomass o f any oth e r species o f Juncus.
Shoot to "root" tr a n s lo c a tio n , occurring during the e a rly
summer, undoubtedly represents the movement o f carbohydrates

76

produced in excess o f the capacity o f the leaves to u t i l i z e or store
them.

Increased below ground storage in Typha s p p ., evidenced a t the

onset o f f a l l dormancy, has been s i m i l a r l y in te r p r e te d by J e rv is
(1 9 6 9 ), who suggests th a t decreased r e s p ir a to ry a c t i v i t y in the f a l l
allows g re a te r net production a t th a t tim e.

Although some downward

tra n s lo c a tio n was evidenced during the f a l l

in the dune pond study,

below ground biomass accrual was balanced by above ground biomass
lo s s , and I have not considered t h is accumulation to be net produc­
t io n .
Late season below ground biomass accumulation may represent
a s tra te g y f o r s u rv iv a l whereby curren t above ground s tru c tu re is
r e s o l u b i l i z e d , tra n s p o rte d , and stored in below ground organs f o r
m etabolic use during the w in te r or f o r the reform ation o f photosyn­
t h e t i c organs a t the beginning o f the next y e a r 's growing season.
Such a s tra te g y would l i k e l y be o f great value p a r t i c u l a r l y fo llo w in g
periods o f s i g n i f i c a n t loss (35%) o f macrophyte biomass as evidenced
between 1973 and 1974.
"Root" to shoot tr a n s lo c a t io n , continued production o f new
shoots, "root" r e s p ir a t i o n , and m o r t a l it y were a l l l i k e l y responsible
f o r the mid through l a t e summer d e p letio n o f below ground biomass
s to re s .

Discussion o f tra n s lo c a tio n processes in aquatic plants with

refe re n c e to the r o le o f roots and other submerged organs (S culthorpe,
1967; Bristow and Whitcombe, 1971; among o thers) has been la r g e ly
li m i t e d to the absorption and u t i l i z a t i o n o f inorganic n u tr ie n ts .
In a s im il a r c o n te x t, the tra n s lo c a tio n o f carbohydrates has been
discussed f o r t e r r e s t r i a l grasses ( f o r example, Smith and Leinweber,

77
1971; Singh and Coleman, 1974) and crop plants (M ilth o rp e and
Moorby, 1974).

Although the macrophyte community became in c re a s in g ly

dominated by o ld e r shoots as the growing season progressed, new
shoots were c o n tin u a lly produced, re p la c in g losses o f the o ld e r due
to damage and m o r t a l it y .

As demonstrated by the harvested p lo t gas

exchange experiments, the dominant r e s p ir a to r y component o f the pond,
during the growing season, was the below ground macrophyte biomass.
High le v e ls o f r e s p ir a to r y a c t i v i t y were l i k e l y a t t r i b u t a b l e to
e ne rge tic demands imposed on the rooted organs in maintaining
m e ristem atic, tr a n s lo c a t io n , and absorption processes.
Ash content estim ates, compared to published values
tabu late d by Westlake (1 9 6 5 ), are s im il a r to those presented f o r
sedges and grasses, but are somewhat lower than the content l i s t e d
f o r other a quatic p la n ts .

Ash content o f the l i v i n g shoots, ranging

between 2 and 4% o f the dry w eig ht, compared most c lo s e ly w ith t h a t
o f Juncus effusus (Boyd, 1971) which contains between 3 and 5% ash
on a dry weight basis.

Westlake's contention (op. c i t . ) concerning

the lack o f seasonal v a ria tio n s in the ash content o f freshwater
p la n ts , apparently a p p lic a b le to the above ground biomass, was not
j u s t i f i e d in t h is study w ith respect to below ground m a te r ia l.
Seasonal v a ria tio n s in the ash content o f the below ground biomass
(7% change in 1973 and 6% change in 1974) may be r e la t e d to patterns
o f tra n s lo c a tio n and mineral a v a i l a b i l i t y , although no data are a v a i l ­
able to examine these p o s s i b i l i t i e s .
The c a lc u la tio n o f macrophyte p r o d u c t iv it y , based on changes
in below ground biomass (see r e s u lt s ) seems to be unique to t h is

78
study.

Moreover the observed p a tte rn o f s ig n i f i c a n t below ground

biomass accrual during the e a r ly summer, counters t h a t observed in
the few wetland studies in which below ground biomass estimates have
been made ( f o r example, see Westlake, 1966; J e r v is , 1969; Bernard,
1974a, 1974b).

In the studies c ite d here, below ground biomass peaks

were reported in the f a l l , minima occurring during the e a r ly summer
fo llo w in g a period o f rapid spring d e p le tio n .

I t is not known

whether the reverse o f t h i s p a tte rn (as reported f o r Juncus b a l t i c u s )
represents a species c h a r a c t e r i s t i c , or an adaptation f o r existence
in dune pond h a b ita ts .

Perhaps an annual study o f the dynamics o f

"root" growth o f t h is species in a d i f f e r e n t h a b ita t would resolve
th is question.
In s p ite o f various confounding fa c to rs and technical d i f ­
f i c u l t i e s in vo lv e d , the harvest (biomass) approach used to estim ate
the p r o d u c tiv ity o f macrophytes in t h i s study remains the most
commonly used, and perhaps the most accurate (Wetzel and Hough,
1973).

Most s u ita b le in estim ating the p r o d u c tiv ity o f p la n t popula­

tio n s demonstrating n e g lig ib le losses between sampling periods
(Westlake, 1963, 1965), the harvest technique has also been adapted
to populations subject to high m o r t a l it y (Mathews and Westlake, 1969).
As w i l l be subsequently discussed, a major drawback o f t h is technique
is i t s l i m i t a t i o n to the measurement o f la rg e p a r t ic u la t e m a tte r,
turnover estimates being e m p ir ic a lly based on the accumulation o f
nondecomposed l i t t e r .
A lte r n a te methods f o r determining p r o d u c tiv ity o f aquatic
macrophytes are few and these have been in fr e q u e n tly employed.

79

Moreover, i t appears t h a t our knowledge concerning the physiology
o f submerged macrophytes, p a r t i c u l a r l y in regard to in te r n a l gas
exchange ( c f . Hartman and Brown, 1967; Hough, 1974), has lagged
methodological advances in p r o d u c t iv it y analyses based on in s itu
metabolic techniques.

Recently Wetzel and Hough (1973) have

emphasized th a t estimates based on oxygen change and radio-carbon
methods may be o f questionable value or t o t a l l y erroneous.

Ecosystem Metabolism
During the annual period o f October 1973 through October
1974, a P/R r a t i o o f 1.45 was e s tim ated, r e f l e c t i n g the annual net
o

ecosystem production o f approximately 6 1 .8 gmC/m

(Table 1 7 ).

If

based only on the macrophyte biomass and l i t t e r , considered c o ll e c ­
t i v e l y , t h is amount o f production would represent an annual increase
in macrophyte m a te ria l o f approximately 10% over estimates made in
October 1973.

However, when based on t o t a l ecosystem organic mass,

in cluding the biomass o f oth e r l i v i n g components (algae and animals)
as well as dissolved and p a r t ic u la t e d e t r i t a l mass in a d d itio n to
macrophyte l i t t e r ,

2

6 1.8 gmC/m

accumulation undoubtedly represents

considerably less than 10% annual a c c ru a l.
Considering the q u a n t it a t iv e importance and rapid turnover
c h a r a c t e r is t ic s o f dissolved organic m atter (D .O .M .) in aquatic
systems (Wetzel e t a l . ,

19 72 ), an attempt to balance the carbon

budget ( i . e . , e x p la in d e v ia tio n from P/R = 1 .0 ) based on p a r t ic u la t e
mass would be r e l a t i v e l y meaningless.

Indeed net ecosystem produc­

tio n in t h is study cannot be accounted f o r on the basis o f increased

80
Table 17.

Annual Carbon B u d g e t ^

For The Dune Pond.

2
gmC/m /y e a r
199.5

Gross Photosynthesis
Autotrophic Respiration

72.7

Net Photosynthesis:
Macrophyte
E p ip e lic Periphyton
Phytoplankton
Total

77.4
32.4
17.0
126.8

H eterotrophic Respiration

65.0

Net Ecosystem Production

61.8

^ It

is assumed t h a t allochthonous inputs are n e g l ig i b le .

macrophyte biomass or l i t t e r .

Assuming t h a t p a r t ic u la t e losses ( i . e . ,

herbivory and oth e r sources o f export) were sm all, D.O.M. loss (not
measured) may account f o r the 6 1 .8 gmC/m / y r . not respired autochthonously.

Changes in the water t a b le in response to flu c u a tio n s

in the water le v e l o f Lake Michigan (see r e s u lt s ) may have been
important in seasonally flu s h in g the pond.
Net ecosystem production represented a s i g n i f i c a n t portion
(49%) o f annual net primary production (Table 1 7 ).

Changes in the

c apacity o f the pond to e i t h e r re s p ire (51%) or export (49%) net
primary production, presumably in a d e t r i t a l form, would be r e fle c t e d
in changes in both net ecosystem p r o d u c tiv ity and the P/R r a t i o .
Non r e s p ir a to r y loss o f p e r e n n ia lly maintained biomass would not
a f f e c t these c h a r a c t e r is t ic s however, both o f which are c a lc u la te d
on the basis o f production and not biomass.

With th is point in mind,

81

the s i g n if ic a n t reduction (35%) in macrophyte biomass (below ground),
which occurred during the summer o f 1973, may have had no e f f e c t on
the P/R r a t i o (undetermined) a t t h a t tim e.
T illy

(1968) c it e s estimates o f a s s im ila tio n e f f ic ie n c y

from a number o f aquatic s tu d ie s .

These range from 0.2% f o r Root

Spring ( T e a l, 1957) to 8.0% f o r S i l v e r Springs, F lo rid a (Odum, 1957).
The annual a s s im ila tio n e f f ic ie n c y c a lc u la te d f o r the dune pond
(GPP/L = 0.42%, where L = o n e -h a lf s o la r incidence a t the pond sur­
fa c e)
c it e d .

fa lls

w ith in t h is range but is somewhat lower than most

E ff ic ie n c ie s g re a te r than 10%, observed under manipulated

conditions (Thomas, 1955; M c ln tire and Phinney, 1965 ), are uncommon
and g e n e ra lly can be explained by the very low l i g h t i n t e n s i t ie s
used.

Low e f f i c i e n c i e s are expected under natural conditions since

l i g h t s a tu ra tio n u sually excludes a s i g n i f i c a n t amount o f in c id e n t
l i g h t from usage.

Aside from physio log ical con s id e ra tio n s , a s s im ila ­

tio n e f f i c i e n c y , when measured on an areal basis under natural
cond itio n s , is dependent upon the t o t a l surface a v a ila b le f o r photo­
synthesis.

This surface can lo osely be considered a function o f

standing crop per u n it area.

The r e l a t i v e l y low standing crop in

the dune pond is thought to be an important f a c t o r in li m i t i n g
a s s im ila tio n e f f ic ie n c y .
The phenomenon o f p h o to re s p ira tio n , well known in t e r ­
r e s t r i a l plants (Hatch e t a l . ,

1971; Z e l i t c h , 1971) has re c e n tly

been examined in submerged a quatic plants (Hough and W etzel, 1972;
Hough, 1974).

Gas exchange methods f o r estim atin g photosynthesis

g e n e ra lly do not d is tin g u is h between mitochondrial

(dark) r e s p ir a tio n

82
and p h o to re s p ira tio n .

By f a i l i n g to compensate f o r the p h o toresp ira-

to ry e f f e c t on the C02 concentration o f the l i g h t chamber, gross
photosynthesis, corrected only f o r dark r e s p ir a to r y a c t i v i t y , was
p o t e n t i a l l y underestimated in th is study.

The e x te n t o f such under­

estim ation is unknown and could only have been resolved by
simultaneously measuring rates o f photosynthesis and p h o to re s p ira tio n .
Afternoon depressions in gross photosynthesis observed in
t h is study are c o n s is te n t w ith s im il a r pattern s o f net photosynthetic
depression demonstrated in submerged angiosperms (Hartman and Brown,
1967; Hough, 1974; and o thers) and in phytoplankton populations
(Doty and O g u ri, 1957; and o th e r s ).

Hough and Wetzel (1972) specu­

la te d t h a t "afternoon depressions" in net photosynthesis in aquatic
plants are associated w ith increases in p h o to re s p ira tio n .

I f photo-

r e s p ir a to r y a c t i v i t y is important in determining diurnal patterns
o f net photosynthesis, pattern s o f gross photosynthesis (uncorrected
f o r p h o to re s p ira tio n ) would be expected to mimic those o f n e t.
Observed diurnal v a ria tio n s in gross photosynthesis (dune pond study)
c lo s e ly approximate v a r ia tio n s in net photosynthesis, schem atically
depicted by Hough (1 9 7 4 ).
D ir e c t measurement o f the aqueous C02 f l u x w ith in the meta­
b o lic chambers, was not made during t h is study, as i t was assumed
t h a t the aqueous f l u x (corrected f o r temperature v a r i a t i o n ) could be
estimated from C02 p a r t i a l pressure changes in the o v e rly in g atmos­
pheric volume o f the chambers (see equation 2 in methods).

This

c a lc u la tio n can be c r i t i c i z e d because i t ignores the i n h ib it o r y
e f f e c t o f d i f f u s i v e re sista n c e to C02 exchange across the a ir - w a t e r

83
in te rfa c e .

Th eo re tic a l aspects o f CO2 d iffu s io n are complex, but

have been a pplied to natural systems (Emerson, e t a l . , 1973).
R espiratory r a te determ inations would have been p o t e n t i a l l y under­
estim ated in t h is study during periods o f incubation when the evolu­
tio n o f CO2 w ith in the aqueous volume o f the dark chamber exceeded
C02 evasion in to the gaseous volume.

I t is f e l t however t h a t C02

exchange in the pond was in most cases s u f f i c i e n t l y rapid to minimize
t h i s p o te n tia l source o f e r r o r and i t is assumed t h a t the e r r o r
involved on an annual basis was sm all.

High ra te s o f CC^ exchange

across the a ir - w a t e r in t e r f a c e have been reported in a eutrophic
la k e , o f the Canadian Shield (S c h in d le r e t a l . , 1972) where C02
invasion was found to equal a lg a l net production (S c h in d le r and Fee,
1973) and in an o lig o tr o p h ic a r t i c pond (Coyne and K e lle y , 1974)
where CO2 evasion ra te s were estim ated.

Im p o rta n tly , gross a s s im ila ­

tio n estimates in the dune pond study would not have been a ffe c te d by
t h is p o te n tia l problem, since r e s p ir a to r y underestimates (dark
chamber) would have been balanced by a s s im ila tio n overestimates
( l i g h t chamber), th e re being no net e f f e c t on the c a lc u la tio n o f
gross photosynthesis (dark chamber CO2 f lu x - l i g h t chamber CC^ f l u x ) .

Metabolic Im p lic a tio n s Regarding
Macrophyte P ro d u c tiv ity
As p reviously demonstrated, the rapid accumulation o f below
ground biomass tem porally corresponded to peak a s s im ila to ry a c t i v i t y
(m etabolic measurements) by the macrophytes, both occurring during
the e a r ly summer.

Net below ground biomass production during th is

84
period however, is q u a n t i t a t i v e l y d i f f i c u l t to i n t e r p r e t on the basis
o f observed gross a s s im ila to ry a c t i v i t y (gas exchange d a t a ) .

Calcu­

la tio n s show th a t the magnitude o f net production (in c lu d in g a l g a l )
could be explained on the basis o f measured gross a s s im ila tio n only
i f the r a t i o o f net production to gross a s s im ila tio n approximated
1 .0 during the e a r ly summer.

Although macrophyte r e s p ir a t io n rates

l i k e l y were r e l a t i v e l y low a t t h a t tim e , they c e r t a i n l y could not
have been zero, thus a lt e r n a t e explanations were sought f o r th is
phenomenon.
Evidence e x is ts f o r CC^ absorption by the "roots" o f sub­
merged freshwater plants (Brown, 1913; B ristow , 1969; Wium-Anderson,
19 71 ), y e t q u a n t if ic a t io n o f t h is process o r the e lu c id a tio n o f i t s
importance in photosynthesis, has y e t to be resolved.

The absorption,

t r a n s lo c a t io n , and photosynthetic f i x a t i o n o f CC^ withdrawn from the
s u b s tra te , q u ite obviously confounding gas exchange measurements,
would r e s u lt in underestimated photosynthesis determ inations.

CO2

uptake by the "roots" o f submerged plants may represent an adaptive
advantage in aquatic environments where fr e e CO2 is l i m i t i n g ( i . e . ,
hard water la k e s ).

Such a mechanism would also be valuable to emer­

gent p la n ts , which might become lim it e d by the atmospheric CO2 supply
during periods o f calm a i r and a c tiv e photosynthesis.

I t is o f

course also possible t h a t inadequacies o f the gas exchange method
i t s e l f were responsible f o r the d i s p a r i t y between gas exchange and
harvested estimates o f production noted during the e a r ly summer.
As the magnitude o f auto tro p h ic r e s p ir a t io n becomes la rg e
r e l a t i v e to th a t o f hetero tro p h ic r e s p ir a t i o n , net primary

85
p r o d u c tiv ity (always g re a te r than or equal to net ecosystem produc­
t i v i t y ) can be approximated by metabolic estimates o f net ecosystem
p r o d u c tiv ity ir r e s p e c tiv e o f export losses.

Assuming t h a t these two

p r o d u c tiv ity values approach equivalence in t h is study during mid
to l a t e summer (th e period o f maximum auto tro p h ic r e s p i r a t i o n ) ,
t o t a l net primary p r o d u c t iv it y a t t h a t time can be roughly estimated
on the basis o f the in te g ra te d d iffe r e n c e between a s s im ila tio n and
r e s p ir a tio n curves (Figure 4 ) .

Algal net primary production ( ^ C

estim ate) during t h is period explains only about 60% o f t o t a l net
primary production, c a lc u la te d on the basis o f the above argument,
thus underestimated (h a rv es t es tim ate ) l a t e season net production
by the macrophytes is in d ic a te d .
A u to ly t ic re le as e o f dissolved organic m atter (D .O .M .) by
Scirpus subterminal is has been shown to represent a very s i g n if ic a n t
portion o f the net production (Otsuki and W etzel, 1974).

In th a t

study, estimates were made under both aerobic and anaerobic condi­
t io n s , and 30 to 40% losses were reported to have occurred w ith in
5 days a f t e r tis s u e death.

Since the biomass (h a rv es t) technique is

lim it e d to the measurement o f la rg e p a r t ic u la t e m atter ( l i v i n g b io ­
mass and nondecomposed l i t t e r ) , the release and turnover o f D .O .M .,
o r ig in a t in g from newly formed macrophyte l i t t e r v ia a u t o l y t i c and
( o r ) microbial processes, may have re s u lte d in an underestimate o f
macrophyte net production.
The e x c re tio n o f D.O.M. by l i v i n g submersed macrophytes
has also been shown to be q u a n t i t a t i v e l y important to the measure­
ment o f photosynthetic ra te s (W e tz e l, 1969; Wetzel and Manny, 1971).

86
I fe e l t h a t excre to ry losses o f D.O.M. from the l i v i n g shoots were
probably unimportant in the dune pond however, since n e a rly 70% o f
the shoot biomass was normally located above the a ir - w a t e r i n t e r ­
fac e.

Speculation on below ground D.O.M. loss lacks s u b s ta n tia tio n ,

since data on t h i s p o s s i b i l i t y is n o nexistan t.

Organic leakage from

t h is very important f r a c t i o n o f the macrophyte biomass, might a ffo r d
a c o l l a t e r a l e x p la n a tio n , in a d d itio n to those alread y proposed f o r
the mid through l a t e summer d e p letio n o f below ground storage, as
well as r e s u ltin g in a p o t e n t i a l l y underestimated determ ination o f
macrophyte p r o d u c t iv it y .

Comparisons With Other Studies
Total net primary production e s tim ate s , based on d e ta ile d
a n alysis o f the p r o d u c t iv it y o f component a utotroph ic po pulations,
are r e l a t i v e l y few.

o

Total annual production (1 2 6 .8 gmC/m ) f o r the

dune pond is approxim ately 2 .5 times less than t h a t estimated f o r
eutrophic Borax Lake (W e tze l, 1964 ), but is comparable to o lig o tr o p h ic
Lawrence Lake, the t o t a l annual production o f which was estimated a t
171.2 gmC/m

(Wetzel e t a l . ,

1972).

Compared on the same b a s is , i t

appears t h a t production w ith in a r c t i c ponds (S ta n le y , 1974), s im ila r
in s ize and depth to the dune pond, is approximately 5 times less
than the dune pond e s tim ate .

The production hierarchy o f a utotroph ic

components w ith in the dune pond (macrophytes > periphyton > phyto­
plankton) is also c h a r a c t e r is t ic o f a r c t i c ponds, and t h is p a tte rn
l i k e l y a pplies to the m a jo r ity o f shallow systems, in which macrophyte
establishment is not impeded.

87
Expressed on the basis o f dry weight using appropriate
conversion f a c t o r s , t o t a l net primary production in the dune pond

2

can be approximated a t 300 gm/m

annually.

This value is comparable

to values suggested by W hittaker (1970) f o r temperate grassland and
c o ntinental s h e lf ecosystems.
A review o f p la n t p r o d u c tiv ity by Westlake (1 9 6 3 ), sum­
marizes some o f the data a v a ila b le on phytoplankton production.

2

Annual production o f phytoplankton in the dune pond (1 7 .0 gmC/m )
is approximately 25% o f suggested values f o r ocean and lake phyto­
plankton, and only 15% o f the value suggested f o r coastal phytoplank­
ton.

Comparisons on an areal basis can be misleading however,

p a r t i c u l a r l y in shallow lakes and ponds since the volume o f water
o v e rly in g a given u n it o f area is ofte n much less than the euphotic
e q u iv a le n t in deeper basins.

Expressed on a volum etric b a s is ,

annual phytoplankton production in the pond can be approximated a t
3
4 1.5 gmC/m , which probably exceeds production o f phytoplankton in
many lakes and in the open ocean.
The importance o f l i t t o r a l producers ( i . e . , macrophytes
and periphyton) in basins having a morphometry such t h a t the r a t i o
o f c o lo n iz a b le l i t t o r a l zone to pelagic zone o f production is la r g e ,
must be reemphasized.

Contributions by the macrophytes and periphyton

c o l l e c t i v e l y accounted f o r approximately 87% o f the t o t a l annual
production o f the dune pond.

The importance o f l i t t o r a l producers

has been s i m i l a r l y demonstrated in oth e r basins.

Treated c o l l e c t i v e l y ,

production by the macrophytes and periphyton accounted f o r g re a te r
than 70% o f t o t a l annual production in Borax Lake (W etzel, 1964),

88
Marion Lake (Hargrave, 1969), Lawrence Lake (Wetzel e t a l . , 1972),
Char Lake (Welch and K a l f f , 1974) and an a r c t i c pond (S ta n le y ,
1974).

Since the m a jo rity o f the lakes o f the world are small and

have la rg e l i t t o r a l surfaces a v a ila b le f o r c o lo n iz a t io n , the impor­
tance o f macrophyte vegetation and l i t t o r a l m ic ro flo ra cannot be
ignored in studies concerning lake ecosystem s tru c tu re and fu n c tio n .

LITERATURE CITED

LITERATURE CITED

American Public Health A sso ciation, American Water Works A ssociation,
Water P o llu tio n Control Federation.
1971. Standard methods
f o r the examination o f water and wastewater including bottom
sediments and sludges.
13th Ed. American Public Health
A ssociation.
New York.
769 pp.
A n ita , N

J . , and others.
1963.
Further measurements o f primary
production using a la rg e volume p l a s t ic sphere. Limnol.
Oceanogr. 8 :166-183.

Backhaus

D. 1967. Okologische Untersuchungen an den Aufwuchsalgen
der opersten Donau und ih r e r Q u e llflu s s e . I . Voruntersuchungen. Arch. Hydrobiol. Suppl. 30:364-399.

Bernard, J. M. 1974a.
Seasonal changes in standing crop and primary
production in a sedge wetland and an adjacent dry o l d - f i e l d
in Central Minnesota.
E c o l. 55:350-359.
Bernard, J. M. 1974b. Primary production and l i f e h is to ry o f Carex
l a c u s t r i s . Can. J. Bot. 52:117-123.
Bordeau, P. F . , and G. M. Woodwell. 1965. Measurements o f p lan t
carbon dioxide exchange by in fra r e d absorption under con­
t r o l l e d conditions and in the f i e l d .
In Methodology o f
P lant Eco-Physiology, Proceedings o f the M o n tp e llie r
symposium, UNESCO. P a ris , pp. 283-289.
Boyd, C. E.
1971. The dynamics o f dry m atter and chemical sub­
s tra te s in a Juncus effusus population. Am. M id i. Nat.
8 6 :2 8 -4 5 .
Bray, J. R. 1961. An estim ate o f a minimum quantum y i e l d o f photo­
synthesis based on ecologic data.
P lant Physiol. 36:371-373.
Bristow, J. M. 1969. The e f f e c t s o f carbon dioxide on the growth
and development o f amphibious p la n ts .
Can. J. Bot.
47:1803-1807.
1971. The r o le o f roots in the
Bristow, J. M. and M. Whitcombe.
n u t r i t i o n o f aquatic vascular p la n ts . Amer. J. Bot.
5 8 :8 -1 3 .

89

90
Brown, W. H. 1913. The r e la t io n o f the substratum to the growth
o f El odea. P h ilip in e J. S ci. s er. C. 8 :1 -2 0 .
1973. Diatom succession and i n t e r ­
Brown, S. D. and A. P. Austin.
action in l i t t o r a l periphyton and plankton.
Hydrobiologia
43:333-356.
C la rke , G. L.
1946. Dynamics o f production in a marine area.
E c o l. Monogr. 16:232-335.
Cowles, H. C. 1899. The ecological r e la t io n s o f the vegetation on
the sand dunes o f Lake Michigan.
Bot. Gaz. 2 7 :9 5 -1 1 7 ,
167-202, 281-308, 361-391.
Coyne, P. I . and J. J. K elle y .
1974. Carbon d ioxide p a r t i a l
pressures in a r c t i c surface waters.
Limnol. and Oceanog.
19:928-938.
Cummins, K. W. and J. C. Wuycheck. 1971. C a lo ric e quivalen ts f o r
in v e s tig a tio n s in ecological e n e rg e tic s .
M i t t . In t e r n a t .
Verein. Limnol. 18:1-158.
Cummins, K. W. 1974. Struc ture and function o f stream ecosystems.
Bio. S ci. 24:631-641.
Doty, M. S. and M. O guri. 1957. Evidence f o r a photosynthetic
d a il y p e r io d ic it y .
Limnol. Oceanogr. 2 :3 7 -4 0 .
Doty, M. S. and Oguri.
1959. The carbon-fourteen technique f o r
determining primary plankton p r o d u c t iv it y .
P u b l. Staz.
Zo ol. N ap o li, Suppl. 31:70-94.
Emerson, S . , W. Broecker, D. W. Schin dler.
1973. Gas exchange ra te s
in a small lake as determined by the radon method. J.
Fish. Res. Bd. Can. 28:139-155.
Fasset, N. C. 1957. A manual o f Aquatic P la n ts . The U n iv e r s ity o f
Wisconsin Press. Madison, Wisconsin. 405 pp.
Republished 1925.
Forbes, S . A. 1887. The lake as a microcosm.
I l l i n o i s Nat. H is t . Surv. B u ll. 15:537-550.
Forsberg, C.
1959. Q u a n titiv e sampling o f subaquatic v e g e ta tio n .
Oikos 10:233-240.
1927.
In v e s tig a tio n s o f the production
Gaarder, T . , and H. H. Gran.
o f plankton in Oslo Fjord. J. Cons. In t e r n . Explor. Mer.
4 2 :1 -4 8 .
Goldman, C. R . , D. T. Mason, and B. J. B. Wood. 1963. Lig h t i n ju r y
and i n h ib it io n in A n ta rc tic fresh w ater phytoplankton.
Limnol. and Oceanog. 8:313-322.

91

Goldman, C. F. 1968. The use o f absolute a c t i v i t y f o r e lim in a tin g
serious e rro rs in the measurement o f primary p r o d u c tiv it y
w ith C-14. J. Cons. perm. i n t . Explor. Mer. 32:172-179.
Goldsworthy, A.

1970.

P h o to re s p ira tio n .

Bot. Rev. 36:321-340.

Hargrave, B. T. 1969. Epibenthic a lg a l production and community
r e s p ir a tio n in the sediments o f Marion Lake. J. Fish.
Res. Bd. Can. 26:2003-2026.
Hartman, R. T. and D. L. Brown.
1967. Changes in the in te r n a l
atmosphere o f submersed vascular hydrophytes in r e l a t i o n
to photosynthesis.
Ecology 48:252-258.
Hatch, M. D . , C. B. Osmond, and R. D. S la y t e r Eds.
1971.
Photo­
synthesis and p h o to re s p ira tio n .
W iley.
New York.
565 pp.
Heath, 0. V. S. 1969. The Physiological Aspects o f Photosynthesis.
London.
Heinemann. 310 pp.
Hough, R. A . , and R. G. Wetzel.
1972. A ^ C assay f o r photo­
r e s p ir a tio n in aquatic p la n ts .
P la n t P hysiol. 49:987-990.
Hough, R. A.
1974.
Pho torespiration in a quatic p la n ts .
Oceanog. 19:912-927.

Limnol. and

Hunding, C, and B. T. Hargrave. 1973. A comparison o f benthic
microalgal production measured by the 14c and oxygen
methods. J. Fish. Res. Bd. Canada. 30:309-312.
Hutchinson, G. E.
1957. A t r e a t i s e on limnology.
Vol. I Geography,
physics, and chemistry. John Wiley and Sons, In c.
New York.
1015 pp.
Jassby, A. D. and C. R. Goldman.
1974.
Loss ra te s from a lake
phytoplankton community.
Limnol. Oceanog. 19:618-627.
Jonasson, P. M. and H. Mathiesen.
1959.
Measurements o f primary
production in two Danish eutrophic la k e s , Esrom S and Fures.
Oikos 10:137-167.
Jorgensen, E. G. 1957.
Diatom p e r io d ic it y and s ili c o n a s s im ila t io n .
Danskbot. Ark.
18(1) 55 pp.
J e r v is , R. A. 1969. Primary production in the freshw ater marsh eco­
system o f Troy Meadows, New Jersey.
B u ll. Torrey Bot. Club
96:209-231.
Kondratyev, K. Ya.
1969. Radiation In The Atmosphere.
Press.
New York.
912 pp.

Academic

92

Lasker, R. and R. W. Holmes. 1957. V a r i a b i l i t y in re te n tio n o f
marine phytoplankton by membrane f i l t e r s .
Nature 180:
1295-1296.
Lemon, E . , L. H. A lle n J r . , and L. M u lle r.
1970. Carbon dioxide
exchange o f a t r o p ic a l ra in f o r e s t.
Part I I . Biosci.
20:1054-1059.
Lindeman, R. L.
1942. The trophic-dynamic aspect o f ecology.
Ecology 23:399-418.
M arg alef, Ramon. 1968. Perspectives in Ecological Theory.
o f Chicago Press.
Chicago.
112 pp.

U n iv e rs ity

Mathews, C. P. and D. F. Westlake.
1969.
Estimation o f production
by populations o f higher plants subject to high m o r t a lit y .
Oikos 20:156-160.
M c A llis t e r , C. D ., N. Shah, J. D. H. S tr ic k la n d .
1964. Marine
phytoplankton photosynthesis as a function o f l i g h t
in t e n s i t y : a comparison o f methods. J. Fish. Res. Bd.
Can. 21:159-181.
M c D i f f e t t , Wayne F . , A. E. C arr, and D. L. Young. 1972. An estim ate
o f primary production in a Pennsylvania t r o u t stream using
a diurnal oxygen curve technique. Amer. Midland Nat.
8 7 ( 2 ) :564-570.
M c ln t i r e , C. D. and H. K. Phinney.
1965.
Laboratory studies o f
periphyton production and community metabolism in l o t i c
environments.
Ecol. Monogr. 35:237-258.
Mcleod, K. W. 1974. Survival s tra te g y o f Ptelea t r i f o l i a t a during
establishment on Lake Michigan sand dunes. A Ph.D. d i s ­
s e r t a t io n .
Michigan State U n iv e r s ity .
McNaughton, S. J.
1973.
Comparative photosynthesis o f Quebec and
C a l if o r n i a ecotypes o f Typha l a t i f o l i a . Ecol. 54:1260-1270.
M ilth o rp e , F. L. and J. Moorby.
1974. An In tro d u c tio n to Crop
Physiology.
Cambridge U n iv e rs ity Press. New York. 202 pp.
Mooney, H. A . , E. L. Dunn, A. T. H arrison , P. A. Morrow, B. Bartholomew,
and R. L. Hays.
1971. A mobile la b o ra to ry f o r gas exchange
measurements. Photosynthetica 5:128-132.
Odum, E. P. 1962.
R elationships between s tru c tu re and function in
the ecosystem. Japan J. Ecol. 12-108-118.
Odum, E. P. 1963.
Primary and secondary energy flow in r e la t io n to
ecosystem s tru c tu re .
Proc. 16th I n t . Cong. Z o o l. 4:336-338.

93
Odum, H.

T. 1956. Primary production in flow ing w aters.
Oceanog. 1:102-117.

Odum, H.

T. 1957.
Springs.

Limnol.

Trophic s tru c tu re and p r o d u c tiv ity o f S i l v e r
Ecol. Monogr. 27:55-112.

Olson, J. S. 1958.
Rates o f succession and s o il changes on southern
Lake Michigan sand dunes. Bot. Gaz. 119:125-170.
Osman, A. M ., and F. L. M ilth o rp e .
1971. Photosynthesis
o f wheat
leaves in r e la t io n to age, illum inance and n u t r ie n t supply.
I I . Results.
Photosynthetica 5 :6 1 -7 0 .
O ts^ ki, A. and R. G. Wetzel.
1974. Release o f dissolved organic
m atter by a u to ly s is o f a submersed macrophyte, Scirpus
subterminal i s . Limnol. Oceanogr. 19:842-845.
Pamatmat, M. M. 1968. Ecology and metabolism o f a benthic community
on an i n t e r t i d a l s a n d fla t.
I n t . Rev. H ydrobiol. 53:211-298.
Penfound, W. T.
1956.
Primary production o f vascular aquatic
p la n ts .
Limnol. Oceanogr. 1 :92-101.
Pieczynska, E. and I . Spodniewska. 1963. Occurrence and c o lo n iz a ­
t io n o f periphyton organisms in accordance w ith the type
o f substra te.
Ekologia Polska. Ser. A. 11:533-545.
Pomeroy, L. R. 1959. Algal p r o d u c tiv ity in s a l t marshes o f Georgia.
Limnol. and Oceanog. 4:386-397.
Rabinowitch, E. I .
Vol. I .

1951. Photosynthesis and r e la te d processes.
In te rs c ie n c e . New York.
599 pp.

Rich, P. H , , R„ G. W etzel, and N. V. Thuy.
1971.
D is trib u tio n ,
production, and r o le o f aquatic macrophytes in a southern
Michigan marl la k e .
Freshwat. B io l. 1 :3 -2 1 .
R uttn e r, F.
1952.
Fundamentals o f Limnology. U n iv e r s ity o f
Toronto Press. Toronto, Canada.
295 pp.
Ryther, J. H. 1954. The r a t i o o f photosynthesis to r e s p ir a t io n in
marine plankton algae and i t s e f f e c t upon the measurement
o f p r o d u c tiv ity .
Deep-Sea Res. 2:134-139.
S c h in d le r, D. W., G. J. B r u n s k ill, S. Emerson, W. Broecker, and T. H.
Peng.
1972. Atmospheric carbon dio x id e :
i t s r o le in
m aintaining phytoplankton standing crops.
Science 177:
1192-1194.
S c h in d le r, D. W. and E. J. Fee. 1973. Diurnal v a r ia t io n o f dissolved
inorganic carbon and i t s uye in estim ating primary produc­
tio n and CO2 invasion in lake 227. J. Fish. Res. Bd. Can.
30:1501-1510.

94
Sculthorpe, C. D. 1967. The Biology o f Aquatic Vascular P la n ts .
Edward Arnold (P ub lishers) Ltd.
London. 610 pp.
S h e lfo rd , V. E. 1911. Ecological succession.
B io l. B u ll. 21:127-151.

II.

Pond fis h e s .

Singh, J. S. and D. C. Coleman.
1974.
D is t r ib u t io n o f photo­
assim ila te d '^carbon in the root system o f a shortgrass
p ra irie .
J. o f Ecol. 62:359-366.
Smith, A. E. and C. L. Leinweber.
1971.
R ela tio n s h ip o f carbo­
hydrate trend and morphological development o f l i t t l e
bluestem t i l l e r s .
Ecol.
52:1052-1057.
S ta n le y , D. W. 1974. Production ecology o f e p ip e l ic algae in
Alaskan tundra ponds. A Ph.D. d is s e r t a t i o n .
North
Carolina State U n iv e rs ity .
Steemann N ie ls e n , E. 1951. Measurement o f the production o f
organic m atter in the sea by means o f carbon 14. Nature
167:684-685.
/ 14\
Steemann N ie ls e n , E. 1952. The use o f r a d io a c tiv e carbon (C ) f o r
measuring organic production in the sea. J. Cons. i n t .
E x pl. Mer. 18:117-140.
Steemann N ie ls e n , E. 1955. The in t e r a c t io n o f photosynthesis and -j^
re s p ir a tio n and i t s importance f o r the determ ination o f C
d is c rim in a tio n in photosynthesis.
P hy s io l. P la n t.
8:945-953.
S t r ic k la n d , J. D. H. 1960. Measuring the production o f marine
phytoplankton.
B u ll. Fish. Res. Bd. Can. 122. 172 pp.
T a i l i n g , J. F. 1957.
Photosynthetic c h a r a c t e r is t ic s o f some f r e s h ­
water plankton diatoms in r e l a t i o n to underwater r a d ia t io n .
New P h y to l. 56:29-50.
T a i l i n g , J. F. 1961.
Photosynthesis under na tu ra l cond itio ns.
Rev. P lant Physiol. 12:133-154.

Ann.

T e a l, J. M. 1957. Community metabolism in a temperate cold spring.
Ecol. Monogr. 27:283-302.
Thomas, M. D. 1955. E ffe c t o f e colog ical fa c to rs on photosynthesis.
Ann. Rev. P lant Physiol. 6 :1 35 -1 5 6.
T i l l y , L. J.
1968. The s tru c tu re and dynamics o f cone spring.
Monogr. 38:168-197.

Ecol

T ip p e t t ,

R. 1970. A r t i f i c i a l surfaces as a method o f studying
populations o f benthic m icro-algae in fresh w ater.
B rit.
Phycol. J. 5 :1 87-199.

U. S. Department o f Commerce. N0AA--National Ocean Survey, Lake
Survey Center.
630 Federal B u ild in g , D e t r o i t , Michigan.
Verduin,

J.
1952. The volume based photosynthetic rates o f aquatic
p la n ts . Amer. J. Bot. 39:157-159.

Verduin,

J.
1956. Primary production in lakes.
1 :8 5-9 1 .

Limnol. Oceanog.

Vollenw eider, R’. A. ( E d . ) .
1969. A Manual on Methods f o r Measuring
Primary Production in Aquatic Environments. Section 3.3 1 .
Blackwell S c i e n t i f i c .
Oxford and Edinburgh.
213 pp.
Welch, H. E. and J. K a l f f .
1974. Benthic photosynthesis and r e s p ir a ­
tio n in Char Lake. J, Fish. Res. Bd. Can. 31:609-620.
Westlake, D. F.
1963.
38:385-425.

Comparisons o f p la n t p r o d u c t iv it y .

B io l. Rev.

Westlake, D. F.
1965. Some basic data f o r in v e s tig a tio n s o f the
p r o d u c t iv it y o f aqu a tic macrophytes. Mem. 1 s t. I t a l .
I d r o b i o l . 229-248.
Westlake,

D. F.
maxima

1966. The biomass and p r o d u c t iv it y o f Glyceria
I . Seasonal changes in biomass.
J. Ecol. 54:745-753.

Westlake,

D. F.
1968. Methods used to determine the annual produc­
tio n o f reedswamp plants w ith extensive rhizomes.
In
Methods o f p r o d u c t iv it y studies in rootsystems and r h iz o spere organisms.
IBP Root Symposium. Moscow. 1968.
226-234. Navka, Moscow.

W etzel, R. G. 1964. A comparative study o f the primary p r o d u c tiv ity
o f higher aquatic p la n t s , periphyton, and phytoplankton in
a la rg e shallow la k e .
I n t . Rev. ges. H ydrobiol. 4 9 :1 -6 1 .
14
Necessity f o r decontamination o f f i l t e r s in C
W e tze l, R. G. 1965a.
measured rates o f photosynthesis in fres h waters.
Ecology
46:540-542.
W e tze l, R. G. 1965b. Techniques and problems o f primary produc­
t i v i t y measurements in higher aquatic plants and periphyton.
Mem. In s. I d r o b io l. Suppl. 18:147-165.
V a ria tio n s in p r o d u c tiv it y o f Goose and hyperW etzel, R. G. 1966.
eutrophic Sylvan Lakes, Indiana.
In v e s t. Indiana Streams
7:147-184.

96

W etzel, R. G. 1969.
Factors in flu e n c in g photosynthesis and excre tio n
o f dissolved organic m atter by a quatic macrophytes in hard
water lakes.
I n t . Ver. Angew. Limnol. Verh. 1 7:72-85.
W etzel, R. G. and B. A. Manny. 1971.
Secretion o f dissolved
organic carbon and nitrogen by a quatic macrophytes.
Ver. Theor. Angew. Limnol. Verh. 18:162-170.

In t.

Wetzel, R. G ., P. H. Rich, M. C. M i l l e r , and H. L. A lle n .
1972.
Metabolism o f dissolved and p a r t ic u la t e d e t r i t a l carbon
in a temperate hard-water la k e . Men. 1 s t. I t a l . I d r o b io l.
29: Suppl. : 185-243.
W etzel, R. G. and R. A. Hough. 1973.
P r o d u c tiv ity and the r o le o f
aquatic macrophytes in lak e s : An assessment. Pol. Arch.
Hydrobiol. 2 0 :9 -1 9 .
W h ittak e r, R. H. 1970. Communities and ecosystems.
Company. Toronto, Canada.
158 pp.

Macmillan

Wilson, D. and J. P. Cooper.
1969. Apparent photosynthesis and l e a f
characters in r e l a t io n to l e a f p o sitio n and age, among
c ontra s tin g Lolium genotypes.
New P h y to l. 68:645-655.
Wium-Anderson, S. 1971. Photosynthetic uptake o f f r e e CO2 by the
roots o f Lobelia dormanna. P hysiol. P la n t.
25:245-248.
Woodwell, G. M. and R. H. W h ittak e r.
1968.
Primary production in
t e r r e s t r i a l communities. Amer. Z o o l. 8 :1 9 -3 0 .
Z e litc h , I .
1971. Photosynthesis, p h o to re s p ira tio n , and p la n t pro­
d u c tiv ity .
Academic press.
347 pp.